Endoplasmic reticulum stress in the heart: insights into mechanisms and drug targets

Magnesium-assisted hydrogen improves isoproterenol-induced heart failure

Heart failure (HF) is a leading cause of mortality among patients with cardiovascular disease and is often associated with myocardial apoptosis and endoplasmic reticulum stress (ERS). While hydrogen has demonstrated potential in reducing oxidative stress and ERS, recent evidence suggests that magnesium may aid in hydrogen release within the body, further enhancing these protective effects. This study aimed to investigate the cardioprotective effects of magnesium in reducing apoptosis and ERS through hydrogen release in a rat model of isoproterenol (ISO)-induced HF. Magnesium was administered orally to ISO-induced HF rats, which improved cardiac function, reduced myocardial fibrosis and cardiac hypertrophy, and lowered the plasma levels of creatine kinase-MB, cardiac troponin-I, and N-terminal B-type natriuretic peptide precursor in ISO-induced HF rats. It also inhibited cardiomyocyte apoptosis by upregulating B-cell lymphoma-2, downregulating Bcl-2-associated X protein, and suppressing ERS markers (glucose-related protein 78, activating transcription factor 4, and C/EBP-homologous protein). Magnesium also elevated hydrogen levels in blood, plasma, and cardiac tissue, as well as in artificial gastric juice and pure water, where hydrogen release lasted for at least four hours. Additionally, complementary in vitro experiments were conducted using H9C2 cardiomyocyte injury models, with hydrogen-rich culture medium as the intervention. Hydrogen-rich culture medium improved the survival and proliferation of ISO-treated H9C2 cells, reduced the cell surface area, inhibited apoptosis, and downregulated ERS pathway proteins. However, the protective effects of hydrogen were negated by tunicamycin (an inducer of ERS) in H9C2 cells. In conclusion, magnesium exerts significant cardioprotection by mitigating ERS and apoptosis through hydrogen release effects in ISO-induced HF.

Altered protein homeostasis in cardiovascular diseases contributes to Alzheimer's-like neuropathology

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. CVD is known to increase the risk of subsequent neurodegeneration but the mechanism(s) and proteins involved have yet to be elucidated. We previously showed that myocardial infarction (MI), induced in mice and compared to sham-MI mice, leads to increases in protein aggregation, endoplasmic reticulum (ER) stress in both heart and brain, and changes in proteostatic pathways. In this study, we further investigate the molecular mechanisms altered by induced MI in mice, which were also implicated by proteomics of postmortem human hippocampal aggregates from Alzheimer's disease (AD) and cardiovascular disease (CVD) patients, vs. age-matched controls (AMC). We utilized intra-aggregate crosslinking to identify protein-protein contacts or proximities, and thus to reconstruct aggregate "contactomes" (nonfunctional interactomes). We used leave-one-out analysis (LOOA) to determine the contribution of each protein to overall aggregate cohesion, and gene ontology meta-analyses of constituent proteins to define critical organelles, processes, and pathways that distinguish AD and/or CVD from AMC aggregates. We identified influential proteins in both AD and CVD aggregates, many of which are associated with pathways or processes previously implicated in neurodegeneration such as mitochondrial, oxidative, and endoplasmic-reticulum stress; protein aggregation and proteostasis; the ubiquitin proteasome system and autophagy; axonal transport; and synapses.

Human circulatory proteome interaction, oxidative stress-associated signalling and cardiovascular implications during titanium dioxide nanoparticle (TiO2-NP) exposure

The increasing exposure to nanoparticles raises a concern over their toxicity. Incidentally, reactive oxygen species (ROS) are produced as a result of the nanoparticle's physicochemical characteristics and interactions with intracellular elements, primarily enzymes, leading to oxidative stress. In this context, the extent of oxidative stress resulting from the toxicity of titanium dioxide nanoparticles (TiO2-NPs) on the cardiovascular system has not yet been thoroughly investigated. Initially, the gel/label-free proteomics (nLC-HRMS/MS) method was used to examine human serum protein interaction and corona composition. Furthermore, different oxidative stress assays (superoxide, total ROS, mitochondrial ROS, and lipid peroxidation) and cell stress assays (apoptosis, ER stress, mitochondrial dysfunction, autophagy, and hypertrophy) were performed in conjunction with endothelial (rat aortic cells) and cardiomyoblast (H9c2) cell cultures. In addition, expression studies (RT-qPCR and immunofluorescence), kinase signalling, and siRNA-mediated gene knockout (NOX2 and XO) studies were conducted. Alongside, in ovo effects on the heart's antioxidant enzymes (SOD and CAT) and metabolomic pathways (1H NMR) confirmed the involvement of oxidative stress in cardiotoxicity. The present results demonstrate a dose-dependent increase in cytotoxicity via the activation of caspase 3 and 9. The dose-dependent increase and its synergistic relationship with cardiovascular stress signalling (ET-1 and Ang-II) highlight the significant role of oxidative stress in nanoparticle toxicity. In summary, this study expands our understanding of the precise health risks associated with human exposure by establishing a connection between the role of the redox system and molecular stress pathways in TiO2-NPs-induced cardiotoxicity.

Nrf3-Mediated Mitochondrial Superoxide Promotes Cardiomyocyte Apoptosis and Impairs Cardiac Functions by Suppressing Pitx2

BACKGROUND

Myocardial infarction (MI) elicits mitochondria reactive oxygen species (ROS) production and cardiomyocyte (CM) apoptosis. Nrf3 (nuclear factor erythroid 2-related factor 3) has an established role in regulating redox signaling and tissue homeostasis. Here, we aimed to evaluate the role and mechanism of Nrf3 in injury-induced pathological cardiac remodeling.

METHODS

Global (Nrf3-KO) and CM-specific (Nrf3△CM) Nrf3 knockout mice were subjected to MI or ischemia/reperfusion injury, followed by functional and histopathological analysis. Primary neonatal mouse and rat ventricular myocytes and CMs derived from human induced pluripotent stem cells were used to evaluate the impact of Nrf3 on CM apoptosis and mitochondrial ROS production. Chromatin immunoprecipitation sequencing and immunoprecipitation-mass spectrometry analysis were used to uncover potential targets of Nrf3. MitoParaquat administration and CM-specific adeno-associated virus vectors were used to further confirm the in vivo relevance of the identified signal pathways.

RESULTS

Nrf3 was expressed mainly in CMs in healthy human hearts, and an increased level of Nrf3 was observed in CMs within the border zone of infarcted human hearts and murine cardiac tissues after MI. Both global and CM-specific Nrf3 knockout significantly decreased injury-induced mitochondrial ROS production, CM apoptosis, and pathological cardiac remodeling, consequently improving cardiac functions. In addition, cardiac-specific Nrf3 overexpression reversed the ameliorative cardiac phenotypes observed in Nrf3-KO mice. Functional studies showed that Nrf3 promoted neonatal mouse ventricular myocyte, neonatal rat ventricular myocyte, and CMs derived from human induced pluripotent stem cell apoptosis by increasing mitochondrial ROS production. Critically, augmenting mitochondrial ROS with MitoParaquat blunted the beneficial effects of Nrf3 deletion on cardiac function and remodeling. Mechanistically, a redox regulator Pitx2 (paired-like homeodomain transcription factor 2) was identified as one of the main target genes of Nrf3. Specifically, Nrf3 binds to Pitx2 promoter, where it increases DNA methylation through recruiting heterogeneous nuclear ribonucleoprotein K and DNA-methyltransferase 1 complex, thereby inhibiting Pitx2 expression. CM-specific knockdown of Pitx2 blunted the beneficial effects of Nrf3 deletion on cardiac function and remodeling, and cardiac-specific Pitx2 overexpression attenuated MI-induced mitochondrial ROS production and CM apoptosis, as well as preserved cardiac functions after MI.

CONCLUSIONS

Nrf3 promotes injury-induced CM apoptosis and deteriorates cardiac functions by increasing mitochondrial ROS production through suppressing Pitx2 expression. Targeting the Nrf3-Pitx2-mitochondrial ROS signal axis may therefore represent a novel therapeutic approach for MI treatment.

Sinapic Acid Ameliorates Doxorubicin-Induced Cardiotoxicity in H9c2 Cardiomyoblasts by Inhibiting Oxidative Stress Through Activation of the Nrf2 Signaling Pathway

The use of doxorubicin (Dox) is restricted because of its cardiotoxicity, which poses a significant mortality risk for cancer patients, despite being a highly effective antibiotic for treating various types of cancer. Therefore, identifying substances or developing preventive strategies against Dox-induced cardiotoxicity is crucial. This study was conducted to determine whether sinapic acid (SA), a phenolic compound with a range of pharmacological effects, could protect against Dox-induced cardiotoxicity in H9c2 cardiomyoblasts. To investigate the preventive effect of SA, H9c2 cardiomyoblasts treated with Dox were pretreated with SA at various concentrations. SA effectively rescued the cells from Dox-induced cardiotoxicity. Additionally, SA significantly reduced oxidative stress by inhibiting mitochondrial dysfunction and endoplasmic reticulum stress. SA also suppressed the expression of MAPK proteins. As for the underlying mechanism of SA's protective effect against Dox-induced cardiotoxicity, SA activated nuclear factor erythroid-2-related factor (Nrf2) by facilitating its movement from the cytosol to the nucleus and increasing the expression of its target antioxidative genes. In summary, this study demonstrated that SA protects H9c2 cardiomyoblasts from Dox-induced cardiotoxicity by inhibiting oxidative stress by the activation of Nrf2-related signaling pathway. Our findings enhance the development of therapeutic strategies to mitigate cardiac toxicity caused by Dox, highlighting the potential antioxidant effect of SA in Dox-treated H9c2 cardiomyoblasts.

Inhibition of Bif-1 confers cardio-protection in myocardial infarction

Myocardial infarction (MI) remains a major cause of chronic heart failure. Endoplasmic reticulum (ER) stress is an emerging therapeutic strategy to prevent adverse remodeling of the infarcted heart. However, little is known about how Bax-interacting protein 1 (Bif-1), a member of the endophilin B family, is involved in mediating cardiac ER stress in ischemic heart disease. Here, a combination of a left anterior descending coronary artery ligation mouse model and an adenovirus-based transfection strategy was used to investigate the effect of Bif-1 on cardiac remodeling and function after MI. 4-Phenylbutyric acid (4-PBA) was used to understand the role of ER stress in cardiac remodeling. To discover the molecular mechanism, an RNA sequencing study was performed. We found that Bif-1 expression was highly elevated in the heart infarct border zone post-MI and neonatal rat cardiomyocytes treated with oxygen and glucose deprivation. Adenovirus-based knockdown of Bif-1 protected the heart from MI as demonstrated by attenuated maladaptive remodeling and preserved contractile function. ER stress inhibition by 4-PBA alleviated the adverse effects of Bif-1 overexpression on cardiac structure and function. Furthermore, we explored the underlying mechanism by RNA sequencing and identified Bif-1 as a molecule involved in cardiac lipid metabolism. In conclusion, our study identifies Bif-1 as a negative regulator of cardiac protection in MI. Inhibition of Bif-1 alleviates ER stress, which may restore lipid metabolism homeostasis to preserve cardiac function post-MI. Therefore, Bif-1 is a potential novel therapeutic target for ischemic heart disease.NEW & NOTEWORTHY Our study demonstrated that Bif-1 contributes to adverse cardiac remodeling and dysfunction following MI by promoting ER stress. Pharmacological inhibition of ER stress ameliorates cardiac remodeling and dysfunction. In addition, we identified Bif-1 as a negative regulator of cardiac lipid metabolism post-MI, as shown by elevated expression of Acox1, Pla2g7, Acsbg1, Acsl5, Ch25h, and Bcat1 in the heart. These findings suggest that Bif-1 plays a crucial role in cardiac decline post-MI.

Molecular Mechanisms Underlying Heart Failure and Their Therapeutic Potential

Heart failure (HF) is a prominent fatal cardiovascular disorder afflicting 3.4% of the adult population despite the advancement of treatment options. Therefore, a better understanding of the pathogenesis of HF is essential for exploring novel therapeutic strategies. Hypertrophy and fibrosis are significant characteristics of pathological cardiac remodeling, contributing to HF. The mechanisms involved in the development of cardiac remodeling and consequent HF are multifactorial, and in this review, the key underlying mechanisms are discussed. These have been divided into the following categories thusly: (i) mitochondrial dysfunction, including defective dynamics, energy production, and oxidative stress; (ii) cardiac lipotoxicity; (iii) maladaptive endoplasmic reticulum (ER) stress; (iv) impaired autophagy; (v) cardiac inflammatory responses; (vi) programmed cell death, including apoptosis, pyroptosis, and ferroptosis; (vii) endothelial dysfunction; and (viii) defective cardiac contractility. Preclinical data suggest that there is merit in targeting the identified pathways; however, their clinical implications and outcomes regarding treating HF need further investigation in the future. Herein, we introduce the molecular mechanisms pivotal in the onset and progression of HF, as well as compounds targeting the related mechanisms and their therapeutic potential in preventing or rescuing HF. This, therefore, offers an avenue for the design and discovery of novel therapies for the treatment of HF.

Inhibition of vascular smooth muscle cell PERK/ATF4 ER stress signaling protects against abdominal aortic aneurysms

Abdominal aortic aneurysms (AAA) are a life-threatening cardiovascular disease for which there is a lack of effective therapy preventing aortic rupture. During AAA formation, pathological vascular remodeling is driven by vascular smooth muscle cell (VSMC) dysfunction and apoptosis, for which the mechanisms regulating loss of VSMCs within the aortic wall remain poorly defined. Using single-cell RNA-Seq of human AAA tissues, we identified increased activation of the endoplasmic reticulum stress response pathway, PERK/eIF2α/ATF4, in aortic VSMCs resulting in upregulation of an apoptotic cellular response. Mechanistically, we reported that aberrant TNF-α activity within the aortic wall induces VSMC ATF4 activation through the PERK endoplasmic reticulum stress response, resulting in progressive apoptosis. In vivo targeted inhibition of the PERK pathway, with VSMC-specific genetic depletion (Eif2ak3fl/fl Myh11-CreERT2) or pharmacological inhibition in the elastase and angiotensin II-induced AAA model preserved VSMC function, decreased elastin fragmentation, attenuated VSMC apoptosis, and markedly reduced AAA expansion. Together, our findings suggest that cell-specific pharmacologic therapy targeting the PERK/eIF2α/ATF4 pathway in VSMCs may be an effective intervention to prevent AAA expansion.

Targeting P21-Activated Kinase 2 as a Novel Therapeutic Approach to Mitigate Endoplasmic Reticulum Stress in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is linked to prolonged endoplasmic reticulum (ER) stress. P21-activated kinase 2 (Pak2) facilitates a protective ER stress response. This study explores the mechanism and role of Pak2 in HFpEF pathology.

METHODS AND RESULTS

The HFpEF mouse model was established using a high-fat diet combined with the nitric oxide synthase inhibitor Nω-Nitro-l-arginine methyl ester (high-fat diet+Nω-Nitro-l-arginine methyl ester). The model exhibited the typical characteristics of HFpEF (cardiac hypertrophy, diastolic dysfunction with preserved systolic function, and lung edema) as determined by echocardiography and hemodynamic analysis. Terminal deoxynucleotidyl transferase dUTP nick end labeling and dihydroethidium staining results showed that cell death and reactive oxygen species generation were higher in the high-fat diet+Nω-Nitro-l-arginine methyl ester-treated group. Transmission electron microscopy revealed disruption of the ER subcellular structures in the HFpEF mouse model, while western blot analysis confirmed reduced Pak2 phosphorylation and impaired inositol-requiring enzyme 1/X-box binding protein 1 splicing ER stress response signaling. Furthermore, H9c2 cells subjected to the palmitic acid-mediated metabolic stress developed temporal changes in unfolded protein response proteins and Pak2 activity. The inositol requiring enzyme 1/X-box binding protein 1 splicing branch of unfolded protein response was impaired earlier than other branches. Overexpression of Pak2 by adenovirus in H9c2 cells sustained the activation of inositol requiring enzyme 1/X-box binding protein 1 splicing. Pak2 deficiency in the mouse heart accelerated the HFpEF progression, and this phenomenon occurred as early as 10 weeks in Pak2 cardiomyocyte-specific knockout mice. Conversely, adeno-associated virus serotype 9-mediated Pak2 overexpression mitigated HFpEF symptoms, underscoring its protective role against HFpEF progression.

CONCLUSIONS

Pak2 prevents HFpEF progression, exerting cardioprotective effects against ER stress. These insights underscore the therapeutic value of Pak2 in HFpEF.

MMP-2 inhibition attenuates ER stress-mediated cell death during myocardial ischemia-reperfusion injury by preserving IRE1α

Endoplasmic reticulum (ER) stress is one of the major events accompanying myocardial ischemia-reperfusion (IR) injury, as hypoxia and oxidative stress disrupt protein folding in the ER. As a result, the unfolded protein response (UPR) is activated through different sensors including inositol-requiring enzyme 1α (IRE1α) and protein kinase R-like ER kinase (PERK). Failure of the UPR to reduce ER stress induces cellular dysfunction. Matrix metalloproteinase-2 (MMP-2) is a ubiquitous protease that is activated intracellularly in response to oxidative stress and partially localizes near the ER. However, its role in ER homeostasis is unknown. We hypothesized that MMP-2 is involved in the regulation of the UPR and ER stress-mediated apoptosis during IR injury. Isolated mouse hearts subjected to IR injury showed impaired recovery of post-ischemic contractile function compared to aerobically perfused controls. Ventricular extracts from IR hearts had higher levels of glucose-regulated protein-78 and protein disulfide isomerase and lower levels of IRE1α and PERK compared to aerobic controls. MMP-2 inhibitors, ARP-100 or ONO-4817, given 10 min before ischemia, improved cardiac post-ischemic recovery and preserved IRE1α level in hearts subjected to 30 min ischemia/40 min reperfusion. IR also increased the levels of CHOP and mitochondrial Bax and caspase-3 and -9 activities, indicating induction of apoptosis, all of which were attenuated by MMP-2 inhibitors, regardless of the reperfusion time. Immunoprecipitation showed an association between MMP-2 and IRE1α in aerobic and IR hearts. During myocardial IR injury MMP-2 may impair the UPR and induce apoptosis by proteolysis of IRE1α. Inhibition of MMP-2 activity protects against cardiac contractile dysfunction in part by preserving IRE1α and preventing the progression to myocardial cell death.

Cardioprotective Effects of Adiponectin-Stimulated Autophagy

Cardiovascular diseases (CVDs), including heart failure, pose a significant economic and health burden worldwide. Current treatment strategies for heart failure are greatly limited, in that they mainly mitigate symptoms or delay further progression. In contrast, therapies aimed at proactively preventing the onset of heart failure could greatly improve outcomes. Adiponectin is an adipocyte-derived hormone that confers an array of cardioprotective effects. It exerts anti-inflammatory effects, improves metabolic function, mitigates endothelial cell dysfunction, and reduce cardiomyocyte cell death. Furthermore, it has gained increasing attention for its ability to activate autophagy, a conserved cellular pathway that facilitates the degradation and recycling of cell components. The disruption of autophagy has been linked to CVDs including heart failure. Additionally, growing evidence also points to specific forms of autophagy, namely mitophagy and lipophagy, as crucial adaptive responses in protection against CVDs. The protective effects of adiponectin, autophagy, mitophagy, and lipophagy against CVDs along with potential therapeutic implications will be discussed.

Aging triggers mitochondrial, endoplasmic reticulum, and metabolic stress responses in the heart

Introduction

Aging is a multifaceted biological process characterized by a progressive decline in cellular and tissue function. It significantly impacts the cardiovascular system and contributes to the onset of cardiovascular diseases. The mitochondria (mt) and the endoplasmic reticulum (ER) play synergistic roles in maintaining cellular homeostasis and energy production in the heart. Nevertheless, their response to cardiac aging is not well known.

Aim

This study explores mt and ER stress responses and their associated factors, such as metabolic, cellular, and autophagic stress, in cardiac aging.

Methods and Results

We utilized 10- and 25-month-old CBA/CaJ mice to evaluate mt, ER, and their associated factors, such as metabolic, cellular, and autophagic stress responses. We studied the gene expression for mitochondrial biogenesis, mt and ER stress response, autophagy and metabolic markers, and activating transcription factors that mediate cellular stress responses. We found no significant difference in mtDNA content and the mRNA expression of the mt transcription factor, Tfam; however, selective mtDNA genes, such as mt-Cytb and mt-Co2, showed significant induction in 25-month-aged compared to 10-month-young hearts. Interestingly, genes of several mitochondrial stress response proteases and their components, including Lonp1, Yme1l1, Afg3l2, and Spg7, were significantly induced, with a substantial induction of Clpp and Clpx. However, age-associated differences were not observed in the induction of mt chaperones (Hspa9 and Hspd1), but significant induction of Dnaja2, a mitochondrial co-chaperone, was observed. The ER stress transcription factors Xbp1 and Atf6 were markedly induced in aged hearts, accompanied by decreased expression of ER stress chaperone Hsp90b with no change in Hspa5 and Dnajb9 chaperones. However, induction of Dnm1l was significant, whereas Mfn1 and Fis1 were downregulated in contrast to Mfn2, suggesting dysregulated mitochondrial dynamics in the aged heart with no change in autophagy and metabolic stress regulators observed. Furthermore, aged hearts showed significantly increased oxidative damage as evidenced by elevated lipid peroxidation (4-HNE) levels.

Conclusion

These findings demonstrate that aging triggers mt, ER, and oxidative stress in the heart, which over time leads to the accumulation of oxidative damage, causing cellular impairment, highlighting these pathways as potential therapeutic targets for mitigating age-related cardiac dysfunction.

NLRX1 attenuates endoplasmic reticulum stress via STING in cardiac hypertrophy

Endoplasmic reticulum stress-induced cell apoptosis is a pivotal mechanism underlying the progression of cardiac hypertrophy. NLRX1, a member of the NOD-like receptor family, modulates various cellular processes, including STING, NF-κB, MAPK pathways, reactive oxygen species production, essential metabolic pathways, autophagy and cell death. Emerging evidence suggests that NLRX1 may offer protection against diverse cardiac diseases. However, the impacts and mechanisms of NLRX1 on endoplasmic reticulum stress in cardiac hypertrophy remains largely unexplored. In our study, we observed that the NLRX1 and phosphorylated STING (p-STING) were highly expressed in both hypertrophic mouse heart and cellular model of cardiac hypertrophy. Whereas over-expression of NLRX1 mitigated the expression levels of p-STING, as well as the endoplasmic reticulum stress markers, including transcription activating factor 4 (ATF4), C/EBP homologous protein (CHOP) and the ratios of phosphorylated PERK to PERK, phosphorylated IRE1 to IRE1 and phosphorylated eIF2α to eIF2α in an Angiotensin II (Ang II)-induced cellular model of cardiac hypertrophy. Importantly, the protective effects of NLRX1 were attenuated upon pretreatment with the STING agonist, DMXAA. Our findings provide the evidence that NLRX1 attenuates the PERK-eIF2α-ATF4-CHOP axis of endoplasmic reticulum stress response via inhibition of p-STING in Ang II-treated cardiomyocytes, thereby ameliorating the development of cardiac hypertrophy.

L-carnitine ameliorates myocardial injury by alleviating endoplasmic reticulum stress via inhibition of PERK pathway in exertional heatstroke rats

Exertional heatstroke (EHS) is a life-threatening condition with potential for tissues and organs injury, including heart. Effective drug strategies to treat patients with EHS are warranted to unlock the therapeutic potential. Considering the cardioprotective effects of L-carnitine (LC), this study aimed to investigate the effects of LC on EHS-induced myocardial injury in rats and to explore the underlying mechanisms. Here, we found that LC exerted a greater protective effect on EHS-induced cardiac dysfunction and mortality, which also significantly attenuated certain negative effects, including increased myocardial apoptosis, pathological changes, and ultrastructural impairment, enhanced activity levels of such serum enzymes as AST, LDH, CK, and CK-MB, reduced BCL-2 expression, increased the expression of cleaved caspase-3 and the critical endoplasmic reticulum stress (ERS) indices like CHOP and GRP78 in EHS rats. Besides, pretreatment of EHS rats with PBA (4-Phenyl butyric acid), a chemical chaperone that attenuates ERS, restored BCL-2 expression, reduced the protein levels of cleaved caspase-3, CHOP, and GRP78. Furthermore, thapsigargin (TG), which induces ERS, enhanced the expression of BAX, cleaved caspase-3, CHOP, and GRP78, attenuated BCL-2 expression, and enhanced mitochondrial impairment in EHS + LC rats. Mechanismly, the protective effects of LC were mediated, at least partly, by inhibiting the activation of PERK pathway against ERS-associated myocardial damage. These results indicate that supplementation of LC might be a potential strategy to reduce myocardial injury by affecting ERS via inhibiting the PERK pathway against EHS.

The Protective Role of miR-130b-3p Against Palmitate-Induced Lipotoxicity in Cardiomyocytes Through PPARγ Pathway

Excess lipid accumulation in the heart is associated with lipotoxicity and cardiac dysfunction due to excessive fatty acid oxidation. Peroxisome proliferator-activated receptor gamma (PPARγ) modulates the expression of key molecules involved in the FA metabolic pathway. Cardiomyocyte-specific overexpression of PPARγ causes dilated cardiomyopathy associated with lipotoxicity in mice. miR-130b-3p has been shown to be downregulated in the plasma of idiopathic dilated cardiomyopathy patients, but its role in modulating cardiomyocyte lipotoxicity via PPARγ remains unclear. Our objective was to investigate the protective role of miR-130b-3p against palmitate-induced lipotoxicity in cardiomyocytes through the modulation of the PPARγ signaling pathway. Human cardiomyoblasts were treated with palmitate. Intracellular lipid accumulation and expression of PPARγ and its downstream targets (CD36, FABP3, CAV1, VLDLR) were analyzed. Mitochondrial oxidative stress was assessed via MitoTracker Green and Redox Sensor Red staining and expression of CPT1B and SOD2. Endoplasmic reticulum stress and apoptosis were determined by examining GRP78, ATF6, XBP1s, CHOP, and caspase-3 expression. miR-130b-3p overexpression was achieved using transfection methods, and its effect on these parameters was evaluated. Luciferase assays were used to confirm PPARγ as a direct target of miR-130b-3p. Palmitate treatment led to increased lipid accumulation and upregulation of PPARγ and its downstream targets in human cardiomyoblasts. Palmitate also increased mitochondrial oxidative stress, endoplasmic reticulum stress and apoptosis. miR-130b-3p overexpression reduced PPARγ expression and its downstream signaling, alleviated mitochondrial oxidative stress and decreased endoplasmic reticulum stress and apoptosis in palmitate-stimulated cardiomyoblasts. Luciferase assays confirmed PPARγ as a direct target of miR-130b-3p. Our findings suggest that miR-130b-3p plays a protective role against palmitate-induced lipotoxicity in cardiomyocytes by modulating the PPARγ signaling pathway.

Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitors: Guardians against Mitochondrial Dysfunction and Endoplasmic Reticulum Stress in Heart Diseases

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are an innovative class of antidiabetic drugs that provide cardiovascular benefits to both diabetic and nondiabetic patients, surpassing those of other antidiabetic drugs. Although the roles of mitochondria and endoplasmic reticulum (ER) in cardiovascular research are increasingly recognized as promising therapeutic targets, the exact molecular mechanisms by which SGLT2 inhibitors influence mitochondrial and ER homeostasis in the heart remain incompletely elucidated. This review comprehensively summarizes and discusses the impacts of SGLT2 inhibitors on mitochondrial dysfunction and ER stress in heart diseases including heart failure, ischemic heart disease/myocardial infarction, and arrhythmia from preclinical and clinical studies. Based on the existing evidence, the effects of SGLT2 inhibitors may potentially involve the restoration of mitochondrial biogenesis and alleviation of ER stress. Such consequences are achieved by enhancing adenosine triphosphate (ATP) production, preserving mitochondrial membrane potential, improving the activity of electron transport chain complexes, maintaining mitochondrial dynamics, mitigating oxidative stress and apoptosis, influencing cellular calcium and sodium handling, and targeting the unfolded protein response (UPR) through three signaling pathways including inositol requiring enzyme 1α (IRE1α), protein kinase R like endoplasmic reticulum kinase (PERK), and activating transcription factor 6 (ATF6). Therefore, SGLT2 inhibitors have emerged as a promising target for treating heart diseases due to their potential to improve mitochondrial functions and ER stress.

Mechanisms of doxorubicin-induced cardiac inflammation and fibrosis; therapeutic targets and approaches

Doxorubicin plays a pivotal role in the treatment of various malignancies. Despite its efficacy, the cardiotoxicity associated with doxorubicin limits its clinical utility. The cardiotoxic nature of doxorubicin is attributed to several mechanisms, including its interference with mitochondrial function, the generation of reactive oxygen species (ROS), and the subsequent damage to cardiomyocyte DNA, proteins, and lipids. Furthermore, doxorubicin disrupts the homeostasis of cardiac-specific transcription factors and signaling pathways, exacerbating cardiac dysfunction. Oxidative stress, cell death, and other severe changes, such as mitochondrial dysfunction, activation of pro-oxidant enzymes, the renin-angiotensin system (RAS), endoplasmic reticulum (ER) stress, and infiltration of immune cells in the heart after treatment with doxorubicin, may cause inflammatory and fibrotic responses. Fibrosis and inflammation can lead to a range of disorders in the heart, resulting in potential cardiac dysfunction and disease. Various adjuvants have shown potential in preclinical studies to mitigate these challenges associated with cardiac inflammation and fibrosis. Antioxidants, plant-based products, specific inhibitors, and cardioprotective drugs may be recommended to alleviate cardiotoxicity. This review explores the complex mechanisms of doxorubicin-induced heart inflammation and fibrosis, identifies possible cellular and molecular targets, and investigates potential substances that could help reduce these harmful effects.

Potential of natural drug modulation of endoplasmic reticulum stress in the treatment of myocardial injury

Myocardial injury (MI) is a common occurrence in clinical practice caused by various factors such as ischemia, hypoxia, infection, metabolic abnormalities, and inflammation. Such damages are characterized by a reduction in myocardial function and cardiomyocyte death that can result in dangerous outcomes such as cardiac failure and arrhythmias. An endoplasmic reticulum stress (ERS)-induced unfolded protein response (UPR) is triggered by several stressors, and its intricate signaling networks are instrumental in both cell survival and death. Cardiac damage frequently triggers ERS in response to different types of injuries and stress. High levels of ERS can exacerbate myocardial damage by inducing necrosis and apoptosis. To target ERS in MI prevention and treatment, current medical research is focused on identifying effective therapy approaches. Traditional Chinese medicine (TCM) is frequently used because of its vast range of applications and low risk of adverse effects. Various studies have demonstrated that active components of Chinese medicines, including polyphenols, saponins, and alkaloids, can reduce myocardial cell death, inflammation, and modify the ERS pathway, thus preventing and mitigating cardiac injury. Thus, this paper aims to provide a new direction and scientific basis for targeting ERS in MI prevention and treatment. We specifically summarize recent research progress on the regulation mechanism of ERS in MI by active ingredients of TCM.

Tetrahydrocurcumin Attenuates Polymyxin B Sulfate-Induced HK-2 Cells Apoptosis by Inhibiting Endoplasmic Reticulum Stress-Mediated PERK/eIF2α/ATF4/CHOP Signaling Pathway Axis

The clinical application of polymyxin B (PMB) is limited by its nephrotoxic effects, making the reduction of PMB-induced nephrotoxicity has become a pressing concern for clinicians. Tetrahydrocurcumin (THC), known for its beneficial characteristics in biological functions, presents an attractive option for intervention therapy to mitigate PMB-induced nephrotoxicity. However, the underlying mechanism of how THC mitigates PMB-induced nephrotoxicity is still poorly understood. Here, we first evaluated the potential of THC intervention therapy to mitigate PMB-induced nephrotoxicity in an in vitro model of PMB-induced cell injury. Moreover, we demonstrated that THC effectively protected HK-2 cells from PMB-induced apoptosis by using cell counting kit-8 and flow cytometry assay. THC could also suppress PMB-induced endoplasmic reticulum (ER) stress via PERK/eIF2α/ATF4/CHOP pathway. In addition, using PERK inhibitor GSK2606414 to inhibit ER stress also alleviated PMB-induced apoptosis. Taken together, these findings provide novel insights that THC possesses the ability to alleviate PMB-induced nephrotoxicity by inhibiting the ER stress-mediated PERK/eIF2α/ATF4/CHOP axis, which sheds light on the benefits of THC as an intervention strategy to reduce PMB-induced nephrotoxicity, thus providing a potential avenue for improved clinical outcomes in patients receiving PMB treatment.

ER stress improvement by aerobic training or enalapril differently ameliorates pathological cardiac remodeling in obese mice

Overactivation of the classic arm of the renin-angiotensin system (RAS) is one of the main mechanisms involved in obesity-related cardiac remodeling, and a possible relationship between RAS and ER stress in the cardiovascular system have been described. Thus, the aim of this study is to evaluate if activating the protective arm of the RAS by ACE inhibition or aerobic exercise training could overturn diet-induced pathological cardiac hypertrophy by attenuating ER stress. Male C57BL/6 mice were fed a control (SC) or a high-fat diet (HF) for 16 weeks. In the 8th week, HF-fed animals were randomly divided into HF, enalapril treatment (HF-En), and aerobic exercise training (HF-Ex) groups. Body mass (BM), food and energy intake, plasma analyzes, systolic blood pressure (SBP), physical conditioning, and plasma ACE and ACE2 activity were evaluated. Cardiac morphology, and protein expression of hypertrophy, cardiac metabolism, RAS, and ER stress markers were assessed. Data presented as mean ± standard deviation and analyzed by one-way ANOVA with Holm-Sidak post-hoc. HF group had increased BM and SBP, and developed pathological concentric cardiac hypertrophy, with overactivation of the classic arm of the RAS, and higher ER stress. Both interventions reverted the increase in BM, and SBP, and favored the protective arm of the RAS. Enalapril treatment improved pathological cardiac hypertrophy with partial reversal of the concentric pattern, and slightly attenuated cardiac ER stress. In contrast, aerobic exercise training induced physiological eccentric cardiac hypertrophy, and fully diminished ER stress.

Astaxanthin Protects Against H2O2- and Doxorubicin-Induced Cardiotoxicity in H9c2 Rat Myocardial Cells

Astaxanthin (AST) is a carotenoid that has positive effects on various organs and tissues. It also exhibits a cardioprotective action. In this study, the influence of AST on the survival of H9c2 cardiomyocytes under hydrogen peroxide (H2O2)- and doxorubicin (DOX)-induced cardiotoxicity was investigated. Under these conditions, the content of cytosolic Ca2+ was measured, and changes in the area of the mitochondrial mass, as well as in the content of the voltage-dependent anion channel 1 (VDAC1), the autophagy marker LC3A/B, and the pro-apoptotic transcription factor homologous protein (CHOP), were determined. It was found that AST removed the cytotoxic effect of H2O2 and DOX, while cell survival increased, and the mitochondrial mass did not differ from the control. At the same time, a decrease in the content of cytosolic Ca2+ and the restoration of the VDAC1 level to values close to the control were observed. The restoration of the CHOP level suggests a reduction in endoplasmic reticulum (ER) stress in cells. The results allow us to consider AST as a potential agent in the prevention and/or treatment of cardiac diseases associated with oxidative stress.

13-Methylpalmatine improves myocardial infarction injury by inhibiting CHOP-mediated cross-talk between endoplasmic reticulum and mitochondria

Myocardial infarction (MI) is a leading cause of morbidity and mortality worldwide, and endoplasmic reticulum stress (ERS) and mitochondrial Ca2+ overload have been involved in apoptotic cardiomyocyte death during MI. 13-Methylpalmatine (13-Me-PLT) is a natural isoquinoline alkaloid isolated from Coptis chinensis and has not been systematically studied for their potential pharmacological effects in cardiovascular diseases. We conducted the present study to elucidate whether 13-Me-PLT modulates MI pathology in animal MI and cellular hypoxic models, employing state-of-the-art molecular techniques. The results demonstrated that 13-Me-PLT preserved post-ischemic cardiac function and alleviated cardiomyocyte apoptosis. 13-Me-PLT decreased ERS and the communication between ER and mitochondria, which serves as a protective mechanism against mitochondrial Ca2+ overload and structural and functional injuries to mitochondria. Our data revealed mitigating mitochondrial Ca2+ overload and apoptosis by inhibiting CHOP-mediated Ca2+ transfer between inositol 1,4,5-trisphosphate receptor (IP3R) in ER and VDAC1 in mitochondria as an underlying mechanism for 13-Me-PLT action. Furthermore, 13-Me-PLT produced superior effects in alleviating cardiac dysfunction and apoptosis post-MI to diltiazem and palmatine. Collectively, our research suggests that the CHOP/IP3R/VDAC1 signaling pathway mediates ER-mitochondrial Ca2+ transfer and 13-Me-PLT activates this axis to maintain cellular and organellar Ca2+ homeostasis, protecting against ischemic myocardial injury. These findings may offer an opportunity to develop new agents for the therapy of ischemic heart disease.

A comprehensive analysis of the role of native and modified HDL in ER stress in primary macrophages

Introduction

Recent findings demonstrate that high density lipoprotein (HDL) function rather than HDL-cholesterol levels themselves may be a better indicator of cardiovascular disease risk. One mechanism by which HDL can become dysfunctional is through oxidative modification by reactive aldehydes. Previous studies from our group demonstrated that HDL modified by reactive aldehydes alters select cardioprotective functions of HDL in macrophages. To identify mechanisms by which dysfunctional HDL contributes to atherosclerosis progression, we designed experiments to test the hypothesis that HDL modified by reactive aldehydes triggers endoplasmic reticulum (ER) stress in primary murine macrophages.

Methods and results

Peritoneal macrophages were harvested from wild-type C57BL/6J mice and treated with thapsigargin, oxLDL, and/or HDL for up to 48 hours. Immunoblot analysis and semi-quantitative PCR were used to measure expression of BiP, p-eIF2α, ATF6, and XBP1 to assess activation of the unfolded protein response (UPR). Through an extensive set of comprehensive experiments, and contrary to some published studies, our findings led us to three novel discoveries in primary murine macrophages: (i) oxLDL alone was unable to induce ER stress; (ii) co-incubation with oxLDL or HDL in the presence of thapsigargin had an additive effect in which expression of ER stress markers were significantly increased and prolonged as compared to cells treated with thapsigargin alone; and (iii) HDL, in the presence or absence of reactive aldehydes, was unable blunt the ER stress induced by thapsigargin in the presence or absence of oxLDL.

Conclusions

Our systematic approach to assess the role of native and modified HDL in mediating primary macrophage ER stress led to the discovery that lipoproteins on their own require the presence of thapsigargin to synergistically increase expression of ER stress markers. We further demonstrated that HDL, in the presence or absence of reactive aldehydes, was unable to blunt the ER stress induced by thapsigargin in the presence or absence of oxLDL. Together, our findings suggest the need for more detailed investigations to better understand the role of native and modified lipoproteins in mediating ER stress pathways.

Exercise mitigates reductive stress-induced cardiac remodeling in mice

The endoplasmic reticulum (ER) regulates protein folding and maintains proteostasis in cells. We observed that the ER transcriptome is impaired during chronic reductive stress (RS) in cardiomyocytes. Here, we hypothesized that a prolonged moderate treadmill exercise mitigates the RS-induced ER dysfunction and cardiac remodeling in cardiac-specific constitutively active Nrf2 mice (CaNrf2-TG). RNA sequencing showed notable alterations in the ER transcriptome of TG hearts at 4, 12, and 24 weeks (16, 28, and 35 genes, respectively). Notably, the downregulation of ER genes was significant at 12 weeks, and further pronounced at 24 weeks, at which the cardiac pathology is evident. We also observed increased levels of ubiquitinated proteins in CaNrf2-TG hearts across all ages, along with VCP, a marker of ERAD function, at 24 weeks. These findings indicate that constitutive Nrf2 activation and RS impair protein-folding activity and augments ERAD function over time. Exercise intervention for 20 weeks (beginning at 6 weeks of age), reduced cardiomyocyte hypertrophy (from 448 μm2 to 280 μm2) in TG mice, through adaptive remodeling, and preserved the cardiac function. However, while exercise did not influence antioxidants or ER stress protein levels, it significantly improved ERAD function and autophagy flux (LC-I to LC-II) in the TG-EXE hearts. Collectively, our findings underscore the prophylactic potential of exercise in mitigating RS-associated pathology, highlighting its essential role in maintaining cellular proteostasis through ER-independent mechanisms.

Downregulating miR-432-5p exacerbates adriamycin-induced cardiotoxicity via activating the RTN3 signaling pathway

BACKGROUND

Adriamycin (ADR) is a widely used chemotherapy drug in clinical practice and it causes toxicity in the myocardium affecting its clinical use. miR-432-5p is a miRNA primarily expressed in myocardial cells and has a protective effect in the myocardium. We aim to explore the protective effect of miR-432-5p on ADR-caused impaired mitochondrial ATP metabolism and endoplasmic reticulum stress (ERs).

METHOD

The primary cardiomyocytes were obtained from neonatal mice and the ADR was added to cells, meanwhile, a mice model was constructed through intravenous ADR challenge, and expression levels of miR-432-5p were examined. Subsequently, the miR-432-5p was introduced in vitro and in vivo to explore its effect on the activity of mitochondrial ATP synthesis, autophagy, and ER stress. The bioinformatics analysis was performed to explore the target of miR-432-5p.

RESULTS

ADR decreased the expression of miR-432-5p in cardiomyocytes. It also decreases mitochondrial ATP production and activates the ER stress pathway by increasing the expression of LC3B, Beclin 1, cleaved caspase 3, and induces cardiac toxicity. miR-432-5p exogenous supplementation can reduce the cardiotoxicity caused by ADR, and its protective effect on cardiomyocytes depends on the down-regulation of the RTN3 signaling pathway in ER.

CONCLUSION

ADR can induce the low expression of miR-432-5p, and activate the RTN3 pathway in ER, increase the expression of LC3B, Beclin 1, cleaved caspase 3, CHOP, and RTN3, and induce cardiac toxicity.

The detrimental role of galectin-3 and endoplasmic reticulum stress in the cardiac consequences of myocardial ischemia in the context of obesity

The association between cardiac fibrosis and galectin-3 was evaluated in patients with acute myocardial infarction (MI). The role of galectin-3 and its association with endoplasmic reticulum (ER) stress activation in the progression of cardiovascular fibrosis was also evaluated in obese-infarcted rats. The inhibitor of galectin-3 activity, modified citrus pectin (MCP; 100 mg/kg/day), and the inhibitor of the ER stress activation, 4-phenylbutyric acid (4-PBA; 500 mg/kg/day), were administered for 4 weeks after MI in obese rats. Overweight-obese patients who suffered a first MI showed higher circulating galectin-3 levels, higher extracellular volume, and LV infarcted size, as well as lower E/e'ratio and LVEF compared with normal-weight patients. A correlation was observed between galectin-3 levels and extracellular volume. Obese-infarcted animals presented cardiac hypertrophy and reduction in LVEF, and E/A ratio as compared with control animals. They also showed an increase in galectin-3 gene expression, as well as cardiac fibrosis and reduced autophagic flux. These alterations were associated with ER stress activation characterized by enhanced cardiac levels of binding immunoglobulin protein, which were correlated with those of galectin-3. Both MCP and 4-PBA not only reduced cardiac fibrosis, oxidative stress, galectin-3 levels, and ER stress activation, but also prevented cardiac functional alterations and ameliorated autophagic flux. These results show the relevant role of galectin-3 in the development of diffuse fibrosis associated with MI in the context of obesity in both the animal model and patients. Galectin-3 in tandem with ER stress activation could modulate different downstream mechanisms, including inflammation, oxidative stress, and autophagy.

Cardiovascular protection of YiyiFuzi powder and the potential mechanisms through modulating mitochondria-endoplasmic reticulum interactions

Cardiovascular diseases (CVD) remain the leading cause of death worldwide and represent a major public health challenge. YiyiFuzi Powder (YYFZ), composed of Coicis semen and Fuzi, is a classical traditional Chinese medicine prescription from the Synopsis of Golden Chamber dating back to the Han Dynasty. Historically, YYFZ has been used to treat various CVD, rooted in Chinese therapeutic principles. Network pharmacology analysis indicated that YYFZ may exhibit direct or indirect effects on mitochondria-endoplasmic reticulum (ER) interactions. This review, focusing on the cardiovascular protective effects of Coicis semen and Fuzi, summarizes the potential mechanisms by which YYFZ acts on mitochondria and the ER. The underlying mechanisms are associated with regulating cardiovascular risk factors (such as blood lipids and glucose), impacting mitochondrial structure and function, modulating ER stress, inhibiting oxidative stress, suppressing inflammatory responses, regulating cellular apoptosis, and maintaining calcium ion balance. The involved pathways include, but were not limited to, upregulating the IGF-1/PI3K/AKT, cAMP/PKA, eNOS/NO/cGMP/SIRT1, SIRT1/PGC-1α, Klotho/SIRT1, OXPHOS/ATP, PPARα/PGC-1α/SIRT3, AMPK/JNK, PTEN/PI3K/AKT, β2-AR/PI3K/AKT, and modified Q cycle signaling pathways. Meanwhile, the MCU, NF-κB, and JAK/STAT signaling pathways were downregulated. The PERK/eIF2α/ATF4/CHOP, PERK/SREBP-1c/FAS, IRE1, PINK1-dependent mitophagy, and AMPK/mTOR signaling pathways were bidirectionally regulated. High-quality experimental studies are needed to further elucidate the underlying mechanisms of YYFZ in CVD treatment.

Role of Ferroptosis Regulation by Nrf2/NQO1 Pathway in Alcohol-Induced Cardiotoxicity In Vitro and In Vivo

The aim of the present study was to evaluate the cardiotoxic effects of alcohol and its potential toxic mechanism on ferroptosis in mice and H9c2 cells. Mice were intragastrically treated with three different concentrations of alcohol, 7, 14, and 28%, each day for 14 days. Body weight and electrocardiography (ECG) were recorded over the 14 day period. Serum creatine kinase (CK), lactic dehydrogenase (LDH), MDA, tissue iron, and GSH levels were measured. Cardiac tissues were examined histologically, and ferroptosis was assessed. In H9c2 cardiomyocytes, cell viability, reactive oxygen species (ROS), labile iron pool (LIP), and mitochondrial membrane potential (MMP) were measured. The proteins of ferroptosis were evaluated by the western blot technique in vivo and in vitro. The results showed that serum CK, LDH, MDA, and tissue iron levels significantly increased in the alcohol treatment group in a dose-dependent manner. The content of GSH decreased after alcohol treatment. ECG and histological examinations showed that alcohol impaired cardiac function and structure. In addition, the levels of ROS and LIP increased, and MMP levels decreased after alcohol treatment. Ferrostatin-1 (Fer-1) protected cells from lipid peroxidation. Western blotting analysis showed that alcohol downregulated the expression of Nrf2, NQO1, HO-1, and GPX4. The expressions of P53 and TfR were upregulated in vivo and in vitro. Fer-1 significantly alleviated alcohol-induced ferroptosis. In conclusion, the study showed that Nrf2/NQO1-dependent ferroptosis played a vital role in the cardiotoxicity induced by alcohol.

Chlorogenic acid attenuates cardiac hypertrophy via up-regulating Sphingosine-1-phosphate receptor1 to inhibit endoplasmic reticulum stress

AIMS

Cardiac hypertrophy, an adaptive response of the heart to stress overload, is closely associated with heart failure and sudden cardiac death. This study aimed to investigate the therapeutic effects of chlorogenic acid (CGA) on cardiac hypertrophy and elucidate the underlying mechanisms.

METHODS AND RESULTS

To simulate cardiac hypertrophy, myocardial cells were exposed to isoproterenol (ISO, 10 μM). A rat model of ISO-induced cardiac hypertrophy was also established. The expression levels of cardiac hypertrophy markers, endoplasmic reticulum stress (ERS) markers, and apoptosis markers were measured using quantitative reverse transcription PCR and western blotting. The apoptosis level, size of myocardial cells, and heart tissue pathological changes were determined by terminal deoxynucleotidyl transferase dUTP nick-end labelling staining, immunofluorescence staining, haematoxylin and eosin staining, and Masson's staining. We found that CGA treatment decreased the size of ISO-treated H9c2 cells. Moreover, CGA inhibited ISO-induced up-regulation of cardiac hypertrophy markers (atrial natriuretic peptide, brain natriuretic peptide, and β-myosin heavy chain), ERS markers (C/EBP homologous protein, glucose regulatory protein 78, and protein kinase R-like endoplasmic reticulum kinase), and apoptosis markers (bax and cleaved caspase-12/9/3) but increased the expression of anti-apoptosis marker bcl-2 in a dose-dependent way (0, 10, 50, and 100 μM). Knockdown of sphingosine-1-phosphate receptor 1 (S1pr1) reversed the protective effect of CGA on cardiac hypertrophy, ERS, and apoptosis in vitro (P < 0.05). CGA also restored ISO-induced inhibition on the AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1) signalling in H9c2 cells, while S1pr1 knockdown abolished these CGA-induced effects (P < 0.05). CGA (90 mg/kg/day, for six consecutive days) protected rats against cardiac hypertrophy in vivo (P < 0.05).

CONCLUSIONS

CGA treatment attenuated ISO-induced ERS and cardiac hypertrophy by activating the AMPK/SIRT1 pathway via modulation of S1pr1.

A novel BAG5 variant impairs the ER stress response pathway, causing dilated cardiomyopathy and arrhythmia

Pathogenic BAG5 variants recently linked to dilated cardiomyopathy (DCM) prompt further investigation into phenotypic, mutational, and pathomechanistic aspects. We explored the clinical and molecular characteristics of DCM associated with BAG5 variants, uncovering the consistently severe manifestations of the disease and its impact on the endoplasmic reticulum (ER) stress response. The analysis involved three siblings affected by DCM and arrhythmia, along with their four unaffected siblings, their unaffected father, and their mother who exhibited arrhythmia. The parents were consanguineous. Exome and Sanger sequencing identified a novel BAG5 variant, c.444_445delGA (p.Lys149AsnfsTer6), homozygous in affected siblings and heterozygous in parents and unaffected siblings. We generated heterozygous and homozygous Bag5 point mutant knock-in (KI) mice and evaluated cardiac pathophysiology under stress conditions, including tunicamycin (TN) administration. Bag5-/- mice displayed no abnormalities up to 12 months old and showed no anomalies during an exercise stress test. However, following TN injection, Bag5-/- mice exhibited significantly reduced left ventricular fractional shortening (LVFS) and ejection fraction (LVEF). Their cardiac tissues exhibited a notable increase in apoptotic cells, despite non-distinctive changes in CHOP and GRP78 levels. Interestingly, only Bag5 KI male mice demonstrated arrhythmia, which was more pronounced in Bag5-/- than in Bag5+/-males. Here, our study reveals a novel BAG5 mutation causing DCM by impairing the ER stress response, with observed sex-specific arrhythmia differences.

CRISPR Activation Reverses Haploinsufficiency and Functional Deficits Caused by TTN Truncation Variants

BACKGROUND

TTN truncation variants (TTNtvs) are the most common genetic lesion identified in individuals with dilated cardiomyopathy, a disease with high morbidity and mortality rates. TTNtvs reduce normal TTN (titin) protein levels, produce truncated proteins, and impair sarcomere content and function. Therapeutics targeting TTNtvs have been elusive because of the immense size of TTN, the rarity of specific TTNtvs, and incomplete knowledge of TTNtv pathogenicity.

METHODS

We adapted CRISPR activation using dCas9-VPR to functionally interrogate TTNtv pathogenicity and develop a therapeutic in human cardiomyocytes and 3-dimensional cardiac microtissues engineered from induced pluripotent stem cell models harboring a dilated cardiomyopathy-associated TTNtv. We performed guide RNA screening with custom TTN reporter assays, agarose gel electrophoresis to quantify TTN protein levels and isoforms, and RNA sequencing to identify molecular consequences of TTN activation. Cardiomyocyte epigenetic assays were also used to nominate DNA regulatory elements to enable cardiomyocyte-specific TTN activation.

RESULTS

CRISPR activation of TTN using single guide RNAs targeting either the TTN promoter or regulatory elements in spatial proximity to the TTN promoter through 3-dimensional chromatin interactions rescued TTN protein deficits disturbed by TTNtvs. Increasing TTN protein levels normalized sarcomere content and contractile function despite increasing truncated TTN protein. In addition to TTN transcripts, CRISPR activation also increased levels of myofibril assembly-related and sarcomere-related transcripts.

CONCLUSIONS

TTN CRISPR activation rescued TTNtv-related functional deficits despite increasing truncated TTN levels, which provides evidence to support haploinsufficiency as a relevant genetic mechanism underlying heterozygous TTNtvs. CRISPR activation could be developed as a therapeutic to treat a large proportion of TTNtvs.

Expanding the Frontiers of Guardian Antioxidant Selenoproteins in Cardiovascular Pathophysiology

Significance: Physiological levels of reactive oxygen and nitrogen species (ROS/RNS) function as fundamental messengers for many cellular and developmental processes in the cardiovascular system. ROS/RNS involved in cardiac redox-signaling originate from diverse sources, and their levels are tightly controlled by key endogenous antioxidant systems that counteract their accumulation. However, dysregulated redox-stress resulting from inefficient removal of ROS/RNS leads to inflammation, mitochondrial dysfunction, and cell death, contributing to the development and progression of cardiovascular disease (CVD). Recent Advances: Basic and clinical studies demonstrate the critical role of selenium (Se) and selenoproteins (unique proteins that incorporate Se into their active site in the form of the 21st proteinogenic amino acid selenocysteine [Sec]), including glutathione peroxidase and thioredoxin reductase, in cardiovascular redox homeostasis, representing a first-line enzymatic antioxidant defense of the heart. Increasing attention has been paid to emerging selenoproteins in the endoplasmic reticulum (ER) (i.e., a multifunctional intracellular organelle whose disruption triggers cardiac inflammation and oxidative stress, leading to multiple CVD), which are crucially involved in redox balance, antioxidant activity, and calcium and ER homeostasis. Critical Issues: This review focuses on endogenous antioxidant strategies with therapeutic potential, particularly selenoproteins, which are very promising but deserve more detailed and clinical studies. Future Directions: The importance of selective selenoproteins in embryonic development and the consequences of their mutations and inborn errors highlight the need to improve knowledge of their biological function in myocardial redox signaling. This could facilitate the development of personalized approaches for the diagnosis, prevention, and treatment of CVD. Antioxid. Redox Signal. 40, 369-432.

Effect of reactive oxygen, nitrogen, and sulfur species on signaling pathways in atherosclerosis

Atherosclerosis is a chronic inflammatory disease in which fats, lipids, cholesterol, calcium, proliferating smooth muscle cells, and immune cells accumulate in the intima of the large arteries, forming atherosclerotic plaques. A complex interplay of various vascular and immune cells takes place during the initiation and progression of atherosclerosis. Multiple reports indicate that tight control of reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) production is critical for maintaining vascular health. Unrestricted ROS and RNS generation may lead to activation of various inflammatory signaling pathways, facilitating atherosclerosis. Given these deleterious consequences, it is important to understand how ROS and RNS affect the signaling processes involved in atherogenesis. Conversely, RSS appears to exhibit an atheroprotective potential and can alleviate the deleterious effects of ROS and RNS. Herein, we review the literature describing the effects of ROS, RNS, and RSS on vascular smooth muscle cells, endothelial cells, and macrophages and focus on how changes in their production affect the initiation and progression of atherosclerosis. This review also discusses the contribution of ROS, RNS, and RSS in mediating various post-translational modifications, such as oxidation, nitrosylation, and sulfation, of the molecules involved in inflammatory signaling.

Therapeutic Role of Chinese Medicine Targeting Nrf2/HO-1 Signaling Pathway in Myocardial Ischemia/Reperfusion Injury

Acute myocardial infarction (AMI), characterized by high incidence and mortality rates, poses a significant public health threat. Reperfusion therapy, though the preferred treatment for AMI, often exacerbates cardiac damage, leading to myocardial ischemia/reperfusion injury (MI/RI). Consequently, the development of strategies to reduce MI/RI is an urgent priority in cardiovascular therapy. Chinese medicine, recognized for its multi-component, multi-pathway, and multi-target capabilities, provides a novel approach for alleviating MI/RI. A key area of interest is the nuclear factor E2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway. This pathway is instrumental in regulating inflammatory responses, oxidative stress, apoptosis, endoplasmic reticulum stress, and ferroptosis in MI/RI. This paper presents a comprehensive overview of the Nrf2/HO-1 signaling pathway's structure and its influence on MI/RI. Additionally, it reviews the latest research on leveraging Chinese medicine to modulate the Nrf2/HO-1 pathway in MI/RI treatment.

Endoplasmic reticulum stress-mediated cell death in cardiovascular disease

The endoplasmic reticulum (ER) plays a vital function in maintaining cellular homeostasis. Endoplasmic reticulum stress (ERS) can trigger various modes of cell death by activating the unfolded protein response (UPR) signaling pathway. Cell death plays a crucial role in the occurrence and development of diseases such as cancer, liver diseases, neurological diseases, and cardiovascular diseases. Several cardiovascular diseases including hypertension, atherosclerosis, and heart failure are associated with ER stress. ER stress-mediated cell death is of interest in cardiovascular disease. Moreover, an increasing body of evidence supports the potential of modulating ERS for treating cardiovascular disease. This paper provides a comprehensive review of the UPR signaling pathway, the mechanisms that induce cell death, and the modes of cell death in cardiovascular diseases. Additionally, we discuss the mechanisms of ERS and UPR in common cardiovascular diseases, along with potential therapeutic strategies.

Chronic lactate exposure promotes cardiomyocyte cytoskeleton remodelling

We investigated the effect of growing on lactate instead of glucose in human cardiomyocyte assessing their viability, cell cycle activity, oxidative stress and metabolism by a proteomic and metabolomic approach. In previous studies performed on elite players, we found that adaptation to exercise is characterized by a chronic high plasma level of lactate. Lactate is considered not only an energy source but also a signalling molecule and is referred as "lactormone"; heart is one of the major recipients of exogenous lactate. With this in mind, we used a cardiac cell line AC16 to characterize the lactate metabolic profile and investigate the metabolic flexibility of the heart. Interestingly, our data indicated that cardiomyocytes grown on lactate (72 h) show change in several proteins and metabolites linked to cell hypertrophy and cytoskeleton remodelling. The obtained results could help to understand the effect of this metabolite on heart of high-performance athletes.

BFGF attenuates aortic valvular interstitial cell calcification by inhibiting endoplasmic reticulum stress-mediated apoptosis

The potential protective effect of basic fibroblast growth factor (BFGF) on the cardiovascular system has been proposed previously, however, its effect on calcific aortic valve disease (CAVD) and underlying mechanisms have not been elucidated. The valvular interstitial cell (VIC) were isolated from porcine aortic valve leaflets. To investigate the effect of BFGF on osteogenic differentiation of VIC, the osteogenic induced medium (OIM) and BFGF were added. The protein expression level was detected by Western blot, and apoptosis was determined by flow cytometry. The effect of BFGF on CAVD process in vivo was assessed by a rat CAVD model, which was identified by echocardiography and Alizarin red staining. The expression level of BFGF in the aortic valve and serum were significantly upregulated in CAVD patients compared to control group. In addition, exogenous BFGF injection attenuates CAVD process in vivo. The protein markers of osteogenic differentiation, endoplasmic reticulum stress (ERS), and apoptosis were significantly upregulated by culture with OIM. On the contrary, the aforementioned proteins were suppressed after adding 100 ng/mL of BFGF. Inhibition of PI3K/Akt and ERK1/2 pathways by specific inhibitors abolished the protective effect of BFGF. In conclusion, BFGF could alleviate the VIC calcification by inhibiting ERS-mediated apoptosis, which is partly regulated by activation of the PI3K/Akt and ERK1/2 signaling pathways. BFGF may provide a potential avenue for CAVD therapy.

Resistance training up-regulates Smyd1 expression and inhibits oxidative stress and endoplasmic reticulum stress in the heart of middle-aged mice

Persistent oxidative stress and endoplasmic reticulum (ER) stress are the primary mechanisms of age-related cardiovascular diseases. Although exercise training is viewed as an effective anti-aging approach, further exploration is needed to identify the mechanisms and functional targets. In this study, the impact of resistance training (RT) on the expression of Smyd1, the levels of reactive oxygen species (ROS) and the expression of ER stress-related protein in the hearts of mice of different ages were assessed. In addition, the role of Smyd1 in the aging-induced oxidative stress and ER stress were evaluated in d-galactose (D-gal)-treated H9C2 cells. We demonstrated that RT in middle age increased the expression of Smyd1 and restricted heart aging-induced ER stress. Overexpression of Smyd1 restrained oxidative stress and ER stress in D-gal-treated H9C2 cells, while the inhibition of Nrf2 and Smyd1 escalated ER stress. These findings demonstrate that Smyd1 has significant impact in regulating age-related ER stress. RT in middle age can up-regulates Smyd1 expression and inhibits oxidative stress and ER stress in the heart.

Exploring the Regulation and Function of Rpl3l in the Development of Early-Onset Dilated Cardiomyopathy and Congestive Heart Failure Using Systems Genetics Approach

BACKGROUND

Cardiomyopathies, diseases affecting the myocardium, are common causes of congestive heart failure (CHF) and sudden cardiac death. Recently, biallelic variants in ribosomal protein L3-like (RPL3L) have been reported to be associated with severe neonatal dilated cardiomyopathy (DCM) and CHF. This study employs a systems genetics approach to gain understanding of the regulatory mechanisms underlying the role of RPL3L in DCM.

METHODS

Genetic correlation, expression quantitative trait loci (eQTL) mapping, differential expression analysis and comparative functional analysis were performed using cardiac gene expression data from the patients and murine genetic reference populations (GRPs) of BXD mice (recombinant inbred strains from a cross of C57BL/6J and DBA/2J mice). Additionally, immune infiltration analysis was performed to understand the relationship between DCM, immune cells and RPL3L expression.

RESULTS

Systems genetics analysis identified high expression of Rpl3l mRNA, which ranged from 11.31 to 12.16 across murine GRPs of BXD mice, with an ~1.8-fold difference. Pathways such as "diabetic cardiomyopathy", "focal adhesion", "oxidative phosphorylation" and "DCM" were significantly associated with Rpl3l. eQTL mapping suggested Myl4 (Chr 11) and Sdha (Chr 13) as the upstream regulators of Rpl3l. The mRNA expression of Rpl3l, Myl4 and Sdha was significantly correlated with multiple echocardiography traits in BXD mice. Immune infiltration analysis revealed a significant association of RPL3L and SDHA with seven immune cells (CD4, CD8-naive T cell, CD8 T cell, macrophages, cytotoxic T cell, gamma delta T cell and exhausted T cell) that were also differentially infiltrated between heart samples obtained from DCM patients and normal individuals.

CONCLUSIONS

RPL3L is highly expressed in the heart tissue of humans and mice. Expression of Rpl3l and its upstream regulators, Myl4 and Sdha, correlate with multiple cardiac function traits in murine GRPs of BXD mice, while RPL3L and SDHA correlate with immune cell infiltration in DCM patient hearts, suggesting important roles for RPL3L in DCM and CHF pathogenesis via immune inflammation, necessitating experimental validations of Myl4 and Sdha in Rpl3l regulation.

Finding New Targets for the Treatment of Heart Failure: Endoplasmic Reticulum Stress and Autophagy

Heart failure is a progressive disease with an annual mortality rate of about 10% and is the end-stage stage of various heart diseases, which places a huge socioeconomic burden on the healthcare system. The development of heart failure has received increasing attention as a potential way to improve the treatment of this disease. Many studies have shown that endoplasmic reticulum stress and autophagy play an important role in the occurrence and development of heart failure. With the in-depth study of endoplasmic reticulum stress and autophagy, both are considered promising targets for pharmacological interventions to treat heart failure, but the mechanism of heart failure between the two is not clear. This review will highlight the effects of endoplasmic reticulum stress, autophagy, and their interactions in the development and development of heart failure, thereby helping to provide direction for the future development of targeted therapies for patients with heart failure. CLINICAL RELEVANCE: This study explored the new targets for the treatment of heart failure: endoplasmic reticulum stress and autophagy. Targeted drug therapy for endoplasmic reticulum stress and autophagy is expected to provide a new intervention target for the treatment of heart failure.

AMPK Signalling Pathway: A Potential Strategy for the Treatment of Heart Failure with Chinese Medicine

Heart failure (HF) is a complex clinical syndrome that represents the advanced stage of cardiovascular disease, characterized by systolic and diastolic dysfunction of the heart. Despite continuous updates in HF treatment drugs, the morbidity and mortality rates remain high, necessitating ongoing exploration for new therapeutic targets. Adenosine monophosphate-activated protein kinase (AMPK) is the serine/threonine protein kinase which responds to adenosine monophosphate (AMP) levels.Activation of AMPK shifts cellular metabolic patterns from synthesis to catabolism, enhancing energy metabolism in pathological conditions such as inflammation, ischemia, obesity, and aging. Numerous studies have identified AMPK as a vital target for HF treatment, with herbal monomers/extracts and compounds affecting key signaling factors including rapamycin targeting protein (mTOR), silencing regulator protein 1 (SIRT1), nuclear transcription factor E2-related factor 2 (Nrf2), and nuclear transcription factor-κB (NF-κB) through regulation of the AMPK signaling pathway.This modulation can achieve the effects of improving metabolism, autophagy, reducing oxidative stress and inflammatory response in the treatment of heart failure, with the advantages of multi-targeting, comprehensive action and low toxicity.The modulation of the AMPK pathway by Traditional Chinese Medicine (TCM) has emerged as a crucial research direction for the prevention and treatment of HF, but a systematic summary and generalization in this field is lacking. This article provides an overview of the composition, regulation, and mechanism of the AMPK signaling pathway's influence on HF, as well as a summary of current research on the regulation of the AMPK pathway by TCM for HF prevention and treatment. The aim is to serve as a reference for the diagnosis and treatment of HF using TCM and the development of new drugs.

β Cell Stress and Endocrine Function During T1D: What Is Next to Discover?

Canonically, type 1 diabetes (T1D) is a disease characterized by autoreactive T cells as perpetrators of endocrine dysfunction and β cell death in the spiral toward loss of β cell mass, hyperglycemia, and insulin dependence. β Cells have mostly been considered as bystanders in a flurry of autoimmune processes. More recently, our framework for understanding and investigating T1D has evolved. It appears increasingly likely that intracellular β cell stress is an important component of T1D etiology/pathology that perpetuates autoimmunity during the progression to T1D. Here we discuss the emerging and complex role of β cell stress in initiating, provoking, and catalyzing T1D. We outline the bridges between hyperglycemia, endoplasmic reticulum stress, oxidative stress, and autoimmunity from the viewpoint of intrinsic β cell (dys)function, and we extend this discussion to the potential role for a therapeutic β cell stress-metabolism axis in T1D. Lastly, we mention research angles that may be pursued to improve β cell endocrine function during T1D. Biology gleaned from studying T1D will certainly overlap to innovate therapeutic strategies for T2D, and also enhance the pursuit of creating optimized stem cell-derived β cells as endocrine therapy.

RBM25 regulates hypoxic cardiomyocyte apoptosis through CHOP-associated endoplasmic reticulum stress

Ischemic heart failure (HF) is one of the leading causes of global morbidity and mortality; blocking the apoptotic cascade could help improve adverse outcomes of it. RNA-binding motif protein 25 (RBM25) is an RNA-binding protein related to apoptosis; however, its role remains unknown in ischemic HF. The main purpose of this study is to explore the mechanism of RBM25 in ischemic HF. Establishing an ischemic HF model and oxygen-glucose deprivation (OGD) model. ELISA was performed to evaluate the BNP level in the ischemic HF model. Echocardiography and histological analysis were performed to assess cardiac function and infarct size. Proteins were quantitatively and locationally analyzed by western blotting and immunofluorescence. The morphological changes of endoplasmic reticulum (ER) were observed with ER-tracker. Cardiac function and myocardial injury were observed in ischemic HF rats. RBM25 was elevated in cardiomyocytes of hypoxia injury hearts and localized in nucleus both in vitro and in vivo. In addition, cell apoptosis was significantly increased when overexpressed RBM25. Moreover, ER stress stimulated upregulation of RBM25 and promoted cell apoptosis through the CHOP related pathway. Finally, inhibiting the expression of RBM25 could ameliorate the apoptosis and improve cardiac function through blocking the activation of CHOP signaling pathway. RBM25 is significantly upregulated in ischemic HF rat heart and OGD model, which leads to apoptosis by modulating the ER stress through CHOP pathway. Knockdown of RBM25 could reverse apoptosis-mediated cardiac dysfunction. RBM25 may be a promising target for the treatment of ischemic HF.

The Role of Endoplasmic Reticulum Stress in Calcific Aortic Valve Disease

Calcific aortic valve disease (CAVD), which is involved in osteogenic reprogramming of valvular interstitial cells, is the most common form of valve disease. It still lacks effective pharmacologic intervention, as its cellular biological mechanisms remain unclear. Congenital abnormality (bicuspid valve) and older age are considered to be the most powerful risk factors for CAVD. Aortic valve sclerosis (AVS) and calcific aortic stenosis (CAS), 2 subclinical forms of CAVD, represent 2 distinct stages of aortic valve calcification. During the AVS stage, the disease is characterised by endothelial activation/damage, inflammatory response, and lipid infiltration accompanied by microcalcification. The CAS stage is dominated by calcification, resulting in valvular dysfunction and severe obstruction to cardiac outflow, which is life threatening if surgery is not performed in time. Endoplasmic reticulum (ER) stress, a state in which conditions disrupting ER homeostasis cause an accumulation of unfolded and misfolded proteins in the ER lumen, has been shown to promote osteogenic differentiation and aortic valve calcification. Therefore, identifying targets or drugs for suppressing ER stress may be a novel approach for CAVD treatment.

IL-6/gp130/STAT3 signaling contributed to the activation of the PERK arm of the unfolded protein response in response to chronic β-adrenergic stimulation

Prolonged activation of the PERK branch of the unfolded protein response (UPR) promotes cardiomyocytes apoptosis in response to chronic β-adrenergic stimulation. STAT3 plays a critical role in β-adrenergic functions in the heart. However, whether STAT3 contributed to β-adrenoceptor-mediated PERK activation and how β-adrenergic signaling activates STAT3 remains unclear. This study aimed to investigate whether STAT3-Y705 phosphorylation contributed to the PERK arm activation in cardiomyocytes and if IL-6/gp130 signaling was involved in the chronic β-AR-stimulation-induced STAT3 and PERK arm activation. We found that the PERK phosphorylation was positively associated with STAT3 activation. Wild-type STAT3 plasmids transfection activated the PERK/eIF2α/ATF4/CHOP pathway in cardiomyocytes while dominant negative Y705F STAT3 plasmids caused no obvious effect on PERK signaling. Stimulation with isoproterenol produced a significant increase in the level of IL-6 in the cardiomyocyte's supernatants, while IL-6 silence inhibited PERK phosphorylation but failed to attenuate STAT3 activation in response to isoproterenol stimulation. Gp130 silence attenuated isoproterenol-induced STAT3 activation and PERK phosphorylation. Inhibiting IL-6/gp130 pathway by bazedoxifene and inhibiting STAT3 by stattic both reversed isoproterenol-induced STAT3-Y705 phosphorylation, ROS production, PERK activation, IRE1α activation, and cardiomyocytes apoptosis in vitro. Bazedoxifene (5 mg/kg/day by oral gavage once a day) exhibited similar effect as carvedilol (10 mg/kg/day by oral gavage once a day) on attenuating chronic isoproterenol (30 mg/kg by abdominal injection once a day, 7 days) induced cardiac systolic dysfunction, cardiac hypertrophy and fibrosis in C57BL/6 mice. Meanwhile, bazedoxifene attenuates isoproterenol-induced STAT3-Y705 phosphorylation, PERK/eIF2α/ATF4/CHOP activation, IRE1α activation, and cardiomyocytes apoptosis to a similar extend as carvedilol in the cardiac tissue of mice. Our results showed that chronic β-adrenoceptor-mediated stimulation activated the STAT3 and PERK arm of the UPR at least partially via IL-6/gp130 pathway. Bazedoxifene has great potential to be used as an alternative to conventional β-blockers to attenuate β-adrenoceptor-mediated maladaptive UPR.

The DRD2 Antagonist Haloperidol Mediates Autophagy-Induced Ferroptosis to Increase Temozolomide Sensitivity by Promoting Endoplasmic Reticulum Stress in Glioblastoma

PURPOSE

Temozolomide resistance remains a major obstacle in the treatment of glioblastoma (GBM). The combination of temozolomide with another agent could offer an improved treatment option if it could overcome chemoresistance and prevent side effects. Here, we determined the critical drug that cause ferroptosis in GBM cells and elucidated the possible mechanism by which drug combination overcomes chemoresistance.

EXPERIMENTAL DESIGN

Haloperidol/temozolomide synergism was assessed in GBM cell lines with different dopamine D2 receptor (DRD2) expression in vitro and in vivo. Inhibitors of ferroptosis, autophagy, endoplasmic reticulum (ER) stress and cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) were used to validate the specific mechanisms by which haloperidol and temozolomide induce ferroptosis in GBM cells.

RESULTS

In the present work, we demonstrate that the DRD2 level is increased by temozolomide in a time-dependent manner and is inversely correlated with temozolomide sensitivity in GBM. The DRD2 antagonist haloperidol, a butylbenzene antipsychotic, markedly induces ferroptosis and effectively enhances temozolomide efficacy in vivo and in vitro. Mechanistically, haloperidol suppressed the effect of temozolomide on cAMP by antagonizing DRD2 receptor activity, and the increases in cAMP/PKA triggered ER stress, which led to autophagy and ferroptosis. Furthermore, elevated autophagy mediates downregulation of FTH1 expression at the posttranslational level in an autophagy-dependent manner and ultimately leads to ferroptosis.

CONCLUSIONS

Our results provide experimental evidence for repurposing haloperidol as an effective adjunct therapy to inhibit adaptive temozolomide resistance to enhance the efficacy of chemoradiotherapy in GBM, a strategy that may have broad prospects for clinical application.

Hypoxia Affects Autophagy in Human Umbilical Vein Endothelial Cells via the IRE1 Unfolded Protein Response

OBJECTIVE

The purpose of this study was to investigate the role of the unfolded protein response, specifically the inositol-requiring enzyme 1 (IRE1) signaling pathway, in hypoxia-induced autophagy in human umbilical venous endothelial cells (HUVECs).

METHODS

The expression of IRE1 and autophagy relative protein in HUVECs with hypoxia was explored by Western blotting, qRT-PCR and confocal microscopy. Further, we evaluated the biological effects of HUVECs by tube formation assay and wound healing assay in vitro. Finally, we examined the function of IRE1 in local blood vessels through animal models.

RESULTS

Hypoxia activated the IRE1 signaling pathway and induced autophagy in a time-dependent manner in HUVECs and further influenced the biological effects of HUVECs. Intraperitoneal injection of IRE1 inhibitors inhibited local vascular autophagy levels and lipid accumulation in model animals.

CONCLUSION

Hypoxia can induce autophagy and activate the IRE1 signaling pathway in HUVECs and the IRE1 signaling pathway is involved in autophagy in hypoxic conditions.

Crosstalk between endoplasmic reticulum stress and non-coding RNAs in cardiovascular diseases

Cells are exposed to various pathological stimulus within the cardiovascular system that challenge cells to adapt and survive. Several of these pathological stimulus alter the normal function of the endoplasmic reticulum (ER), leading to the accumulation of unfolded and misfolded proteins, thus triggering the unfolded protein response (UPR) to cope with the stress or trigger apoptosis of damaged cells. Downstream components of the UPR regulate transcription and translation reprogramming to ensure selective gene expression in response to pathological stimulus, including the expression of non-coding RNAs (ncRNAs). The ncRNAs play crucial roles in regulating transcription and translation, and their aberrant expression is associated with the development of cardiovascular disease (CVD). Notably, ncRNAs and ER stress can modulate each other and synergistically affect the development of CVD. Therefore, studying the interaction between ER stress and ncRNAs is necessary for effective prevention and treatment of CVD. In this review, we discuss the UPR signaling pathway and ncRNAs followed by the interplay regulation of ER stress and ncRNAs in CVD, which provides further insights into the understanding of the pathogenesis of CVD and therapeutic strategies. This article is categorized under: RNA in Disease and Development > RNA in Disease.

Unraveling the roles of endoplasmic reticulum-associated degradation in metabolic disorders

Misfolded proteins retained in the endoplasmic reticulum cause many human diseases. ER-associated degradation (ERAD) is one of the protein quality and quantity control system located at ER, which is responsible for translocating the misfolded proteins or properly folded but excess proteins out of the ER for proteasomal degradation. Recent studies have revealed that mice with ERAD deficiency in specific cell types exhibit impaired metabolism homeostasis and metabolic diseases. Here, we highlight the ERAD physiological functions in metabolic disorders in a substrate-dependent and cell type-specific manner.

ER stress and lipid imbalance drive embryonic cardiomyopathy in a human heart organoid model of pregestational diabetes

Congenital heart defects constitute the most common birth defect in humans, affecting approximately 1% of all live births. The incidence of congenital heart defects is exacerbated by maternal conditions, such as diabetes during the first trimester. Our ability to mechanistically understand these disorders is severely limited by the lack of human models and the inaccessibility to human tissue at relevant stages. Here, we used an advanced human heart organoid model that recapitulates complex aspects of heart development during the first trimester to model the effects of pregestational diabetes in the human embryonic heart. We observed that heart organoids in diabetic conditions develop pathophysiological hallmarks like those previously reported in mouse and human studies, including ROS-mediated stress and cardiomyocyte hypertrophy, among others. Single cell RNA-seq revealed cardiac cell type specific-dysfunction affecting epicardial and cardiomyocyte populations, and suggested alterations in endoplasmic reticulum function and very long chain fatty acid lipid metabolism. Confocal imaging and LC-MS lipidomics confirmed our observations and showed that dyslipidemia was mediated by fatty acid desaturase 2 (FADS2) mRNA decay dependent on IRE1-RIDD signaling. We also found that the effects of pregestational diabetes could be reversed to a significant extent using drug interventions targeting either IRE1 or restoring healthy lipid levels within organoids, opening the door to new preventative and therapeutic strategies in humans.