Novel Insight into the Role of Endoplasmic Reticulum Stress in the Pathogenesis of Myocardial Ischemia-Reperfusion Injury

Endoplasmic reticulum stress in abdominal aortic aneurysm

Abdominal aortic aneurysms (AAAs) are characterized by permanent dilatation of the abdominal aorta, which is accompanied by inflammation, degradation of the extracellular matrix (ECM) and disruption of vascular smooth muscle cell (VSMC) homeostasis. Endoplasmic reticulum (ER) stress is involved in the regulation of inflammation, oxidative stress and VSMC apoptosis, all of which are critical factors in AAA development. Although several studies have revealed the occurrence of ER stress in AAA development, the specific biological functions of ER stress in AAA development remain largely unknown. Given that targeting ER stress is a promising strategy for treating AAAs, further investigation of the physiological and pathological roles of ER stress in AAA development is warranted.

Key subdomains of mesencephalic astrocyte-derived neurotrophic factor attenuate myocardial ischemia/reperfusion injury by JAK1/STAT1/NF-κB signaling pathway

BACKGROUND

Myocardial ischemia/reperfusion (I/R) injury is a common pathological process in clinical practice. Developing effective therapeutic strategies to reduce or prevent this injury is crucial. The article aimed to investigate the role and mechanism of mesencephalic astrocyte-derived neurotrophic factor (MANF) and its key subdomains in modulating myocardial I/R-induced cardiomyocyte apoptosis.

METHODS

MANF stable knockout cell line and MANF mutant overexpression plasmids were constructed. The effects of MANF and mutants on apoptosis and endoplasmic reticulum (ER) stress related proteins were evaluated in hypoxia/reoxygenation-induced HL-1 cardiomyocytes by western blot, immunofluorescence, Tunel and flow cytometry. Echocardiography, ELISA, TTC and Masson were used to observe the effects of recombinant MANF protein (rMANF) on cardiac function in myocardial I/R mice.

RESULTS

This study observed increased expression of MANF in both myocardial infarction patients and I/R mice. MANF overexpression in cardiomyocytes decreased ER stress-induced apoptosis, while MANF knockout exacerbated it. rMANF improved cardiac function in I/R mice by reducing injury and inflammation. This study specifically demonstrates that mutations in the α-helix of MANF were more effective in reducing ER stress and cardiomyocyte apoptosis. Mechanistically, MANF and the α-helix mutant attenuated I/R injury by inhibiting the JAK1/STAT1/NF-κB signaling pathway in addition to reducing ER stress-induced apoptosis.

CONCLUSION

These findings highlight MANF and its subdomains as critical regulators of myocardial I/R injury, offering promising therapeutic targets with significant clinical implications for I/R-related diseases.

Usnic acid alleviates testicular ischemia/reperfusion injury in rats by modulating endoplasmic reticulum stress

Testicular torsion (TT) is a urological condition that can result in infertility in men. The etiopathogenesis of TT includes ischemia/reperfusion injury (IRI) characterized by oxidative stress (OS), inflammation and apoptosis resulting from increased levels of free radicals. Usnic acid (UA), a dibenzofuran, is one of the most common metabolites found in lichens and is known to possess powerful antioxidant properties. The aim of this study was to investigate the potential protective activity of UA in an experimental testicular IRI model for the first time. A total of 18 rats were randomly assigned to three groups (n=6): sham control, IRI and IRI+UA. The IRI groups underwent a four-hour period of ischemia and a two-hour period of reperfusion. The OS, inflammation, endoplasmic reticulum stress (ERS) and apoptosis markers in testicular tissue were evaluated using colorimetric methods. Furthermore, tissue samples were subjected to histological examination, with staining using hematoxylin and eosin. Histopathological findings supported by increased OS, inflammation, ERS and apoptosis levels were obtained in IRI group compared with sham control group. However, UA treatment restored these pathological and biochemical changes. Although this study provides the first preliminary evidence that UA may be used as a useful molecule against testicular IRI, further extensive molecular preclinical studies should be performed before clinical use is considered.

Targeting the Ferroptosis and Endoplasmic Reticulum Stress Signaling Pathways by CBX7 in Myocardial Ischemia/reperfusion Injury

Ferroptosis and endoplasmic reticulum stress (ERS) are common events in the process of myocardial ischemia/reperfusion injury (IRI). The suppression of chromobox7 (CBX7) has been reported to protect against ischemia/reperfusion injury, This research is purposed to expose the impacts and mechanism of CBX7 in myocardial IRI. CBX7 expression was detected using RT-qPCR and western blotting analysis. CCK-8 assay detected cell viability. Inflammatory response and oxidative stress were detected by ELISA, DCFH-DA probe and related assay kits. Flow cytometry analysis and caspase3 activity assay were used to detect cell apoptosis. C11-BODIPY 581/591 staining and ferro-orange staining were used to detect lipid reactive oxygen species (ROS) and Fe2+ level, respectively. Western blotting was used to detect the expression of proteins associated with apoptosis, ferroptosis and ERS. In the hypoxia/reoxygenation (H/R) model of rat cardiomyocytes H9c2, CBX7 was highly expressed. CBX7 interference significantly protected against inflammatory response, oxidative stress, apoptosis, ferroptosis and ERS induced by H/R in H9c2 cells. Moreover, after the pretreatment with ferroptosis activator erastin or ERS agonist Tunicamycin (TM), the protective effects of CBX7 knockdown on the inflammation, oxidative stress and apoptosis in H/R-induced H9c2 cells was partially abolished. To summarize, CBX7 down-regulation may exert anti-ferroptosis and anti-ERS activities to alleviate H/R-stimulated myocardial injury.

Potential role of endoplasmic reticulum stress in doxorubicin-induced cardiotoxicity-an update

As a chemotherapy agent, doxorubicin is used to combat cancer. However, cardiotoxicity has limited its use. The existing strategies fail to eliminate doxorubicin-induced cardiotoxicity, and an in-depth exploration of its pathogenesis is in urgent need to address the issue. Endoplasmic reticulum stress (ERS) occurs when Endoplasmic Reticulum (ER) dysfunction results in the accumulation of unfolded or misfolded proteins. Adaptive ERS helps regulate protein synthesis to maintain cellular homeostasis, while prolonged ERS stimulation may induce cell apoptosis, leading to dysfunction and damage to tissue and organs. Numerous studies on doxorubicin-induced cardiotoxicity strongly link excessive activation of the ERS to mechanisms including oxidative stress, calcium imbalance, autophagy, ubiquitination, and apoptosis. The researchers also found several clinical drugs, chemical compounds, phytochemicals, and miRNAs inhibited doxorubicin-induced cardiotoxicity by targeting ERS. The present review aims to outline the interactions between ERS and other mechanisms in doxorubicin-induced cardiotoxicity and summarize ERS's role in this type of cardiotoxicity. Additionally, the review enumerates several clinical drugs, phytochemicals, chemical compounds, and miRNAs targeting ERS for considering therapeutic regimens that address doxorubicin-induced cardiotoxicity.

Hyperoside reduced particulate matter 2.5-induced endoplasmic reticulum stress and senescence in skin cells

Particulate matter 2.5 (PM2.5) causes skin aging, inflammation, and impaired skin homeostasis. Hyperoside, a flavanol glycoside, has been proposed to reduce the risk of diseases caused by oxidative stress. This study evaluated the cytoprotective potential of hyperoside against PM2.5-induced skin cell damage. Cultured human HaCaT keratinocytes were pretreated with hyperoside and treated with PM2.5. Initially, the cytoprotective and antioxidant ability of hyperoside against PM2.5 was evaluated. Western blotting was further employed to investigate endoplasmic reticulum (ER) stress and cellular senescence and for evaluation of cell cycle regulation-related proteins. Hyperoside inhibited PM2.5-mediated ER stress as well as mitochondrial damage. Colony formation assessment confirmed that PM2.5-impaired cell proliferation was restored by hyperoside. Moreover, hyperoside reduced the activation of PM2.5-induced ER stress-related proteins, such as protein kinase R-like ER kinase, cleaved activating transcription factor 6, and inositol-requiring enzyme 1. Hyperoside promoted cell cycle progression in the G0/G1 phase by upregulating the PM2.5-impaired cell cycle regulatory proteins. Hyperoside significantly reduced the expression of PM2.5-induced senescence-associated β-galactosidase and matrix metalloproteinases (MMPs), such as MMP-1 and MMP-9. Overall, hyperoside ameliorated PM2.5-impaired cell proliferation, ER stress, and cellular senescence, offering potential therapeutic implications for mitigating the adverse effects of environmental pollutants on skin health.

Endoplasmic reticulum stress signaling modulates ischemia/reperfusion injury in the aged heart by regulating mitochondrial maintenance

Aging is associated with an increased risk of myocardial ischemia/reperfusion injury (IRI). With an increasing prevalence of cardiovascular diseases such as coronary arteriosclerosis in older people, there has been increasing interest in understanding the mechanisms of myocardial IRI to develop therapeutics that can attenuate its damaging effects. Previous studies identified that abnormal mitochondria, involved in cellar senescence and oxidative stress, are the master subcellular organelle that induces IRI. In addition, endoplasmic reticulum (ER) stress is also associated with IRI. Cellular adaptation to ER stress is achieved by the activation of ER molecular chaperones and folding enzymes, which provide an important link between ER stress and oxidative stress gene programs. In this review, we outline how these ER stress-related molecules affect myocardial IRI via the crosstalk of ER stress and mitochondrial homeostasis and discuss how these may offer promising novel therapeutic targets and strategies against age-related cardiovascular diseases.

Peptide PDRPS6 attenuates myocardial ischemia injury by improving mitochondrial function

Mitochondrial dynamics play a crucial role in myocardial ischemia-reperfusion (I/R) injury, where an imbalance between fusion and fission processes occurs. However, effective measures to regulate mitochondrial dynamics in this context are currently lacking. Peptide derived from the 40 S ribosomal protein S6 (PDRPS6), a peptide identified via peptidomics, is associated with hypoxic stress. This study aimed to investigate the function and mechanism of action of PDRPS6 in I/R injury. In vivo, PDRPS6 ameliorated myocardial tissue injury and cardiomyocyte apoptosis and decreased cardiac function induced by I/R injury in rats. PDRPS6 supplementation significantly reduced apoptosis in vitro. Mechanistically, PDRPS6 improved mitochondrial function by decreasing reactive oxygen species (ROS) levels, maintaining mitochondrial membrane potential (MMP), and inhibiting mitochondrial fission. Pull-down assay analyses revealed that phosphoglycerate mutase 5 (PGAM5) may be the target of PDRPS6, which can lead to the dephosphorylation of dynamin-related protein1 (Drp1) at ser616 site. Overexpression of PGAM5 partially eliminated the effect of PDRPS6 on improving mitochondrial function. These findings suggest that PDRPS6 supplementation is a novel method for treating myocardial injuries caused by I/R.

Long non-coding RNA-mediated modulation of endoplasmic reticulum stress under pathological conditions

Endoplasmic reticulum (ER) stress, which ensues from an overwhelming protein folding capacity, activates the unfolded protein response (UPR) in an effort to restore cellular homeostasis. As ER stress is associated with numerous diseases, it is highly important to delineate the molecular mechanisms governing the ER stress to gain insight into the disease pathology. Long non-coding RNAs, transcripts with a length of over 200 nucleotides that do not code for proteins, interact with proteins and nucleic acids, fine-tuning the UPR to restore ER homeostasis via various modes of actions. Dysregulation of specific lncRNAs is implicated in the progression of ER stress-related diseases, presenting these molecules as promising therapeutic targets. The comprehensive analysis underscores the importance of understanding the nuanced interplay between lncRNAs and ER stress for insights into disease mechanisms. Overall, this review consolidates current knowledge, identifies research gaps and offers a roadmap for future investigations into the multifaceted roles of lncRNAs in ER stress and associated diseases to shed light on their pivotal roles in the pathogenesis of related diseases.

Exploring the intricacies of calcium dysregulation in ischemic stroke: Insights into neuronal cell death and therapeutic strategies

Calcium ion (Ca2+) dysregulation is one of the main causes of neuronal cell death and brain damage after cerebral ischemia. During ischemic stroke, the ability of neurons to maintain Ca2+ homeostasis is compromised. Ca2+ regulates various functions of the nervous system, including neuronal activity and adenosine triphosphate (ATP) production. Disruptions in Ca2+ homeostasis can trigger a cascade of events, including activation of the unfolded protein response (UPR) pathway, which is associated with endoplasmic reticulum (ER) stress and mitochondrial dysfunction. This response occurs when the cell is unable to manage protein folding within the ER due to various stressors, such as a high influx of Ca2+. Consequently, the UPR is initiated to restore ER function and alleviate stress, but prolonged activation can lead to mitochondrial dysfunction and, ultimately, cell death. Hence, precise regulation of Ca2+ within the cell is mandatory. The ER and mitochondria are two such organelles that maintain intracellular Ca2+ homeostasis through various calcium-operating channels, including ryanodine receptors (RyRs), inositol trisphosphate receptors (IP3Rs), sarco/endoplasmic reticulum calcium ATPases (SERCAs), the mitochondrial Na+/Ca2+ exchanger (NCLX), the mitochondrial calcium uniporter (MCU) and voltage-dependent anion channels (VDACs). These channels utilize Ca2+ sequestering and release mechanisms to maintain intracellular Ca2+ homeostasis and ensure proper cellular function and survival. The present review critically evaluates the significance of Ca2+ and its physiological role in cerebral ischemia. We have compiled recent findings on calcium's role and emerging treatment strategies, particularly targeting mitochondria and the endoplasmic reticulum, to address Ca2+ overload in cerebral ischemia.

Arecoline induces neurotoxicity in HT22 cells via the promotion of endoplasmic reticulum stress and downregulation of the Nrf2/HO-1 pathway

Arecoline, the predominant bioactive substance extracted from areca nut (AN), is the world's fourth most frequently used psychoactive material. Research has revealed that chewing AN can affect the central nervous system (CNS) and may lead to neurocognitive deficits that are possibly linked to the action of arecoline. However, the mechanism behind the neurotoxicity caused by arecoline remains unclear. This study aimed to investigate the neurotoxic effects of arecoline and its underlying mechanism. The results showed that arecoline caused cytotoxicity against HT22 cells in a dose-dependent manner and induced apoptosis by upregulating the expression of pro-apoptotic caspase and Bcl-2 family proteins. Furthermore, arecoline escalated intracellular reactive oxygen species (ROS) levels and Ca2+ concentration with increasing doses, thereby motivating endoplasmic reticulum stress (ERS) and ERS-associated apoptotic protein expression. Additionally, the study found that arecoline attenuates intracellular antioxidant defense by inhibiting the translocation of NF-E2-related factor-2 (Nrf2) into the nucleus and decreasing downstream Heme oxygenase-1 (HO-1) levels. The specific inhibitor Sodium 4-phenylbutyrate (4-PBA) can dramatically attenuate arecoline-mediated cell apoptosis and ERS-associated apoptotic pathway expression by blocking ERS. The antioxidant N-Acetylcysteine (NAC) also effectively reverses the arecoline-mediated increase of ERS-related apoptotic pathway protein levels by scavenging intracellular ROS accumulation. In conclusion, this study suggests that arecoline induces neurotoxicity in HT22 cells via ERS mediated by oxidative stress- and Ca2+ disturbance, as well as by downregulation of the Nrf2/HO-1 pathway.

Melatonin: A potential protective multifaceted force for sepsis-induced cardiomyopathy

Sepsis is a life-threatening condition manifested by organ dysfunction caused by a dysregulated host response to infection. Lung, brain, liver, kidney, and heart are among the affected organs. Sepsis-induced cardiomyopathy is a common cause of death among septic patients. Sepsis-induced cardiomyopathy is characterized by an acute and reversible significant decline in biventricular both systolic and diastolic function. This is accompanied by left ventricular dilatation. The pathogenesis underlying sepsis-induced cardiomyopathy is multifactorial. Hence, targeting an individual pathway may not be effective in halting the extensive dysregulated immune response. Despite major advances in sepsis management strategies, no effective pharmacological strategies have been shown to treat or even reverse sepsis-induced cardiomyopathy. Melatonin, namely, N-acetyl-5-methoxytryptamine, is synthesized in the pineal gland of mammals and can also be produced in many cells and tissues. Melatonin has cardioprotective, neuroprotective, and anti-tumor activity. Several literature reviews have explored the role of melatonin in preventing sepsis-induced organ failure. Melatonin was found to act on different pathways that are involved in the pathogenesis of sepsis-induced cardiomyopathy. Through its antimicrobial, anti-inflammatory, and antioxidant activity, it offers a potential role in sepsis-induced cardiomyopathy. Its antioxidant activity is through free radical scavenging against reactive oxygen and nitrogen species and modulating the expression and activity of antioxidant enzymes. Melatonin anti-inflammatory activities control the overactive immune system and mitigate cytokine storm. Also, it mitigates mitochondrial dysfunction, a major mechanism involved in sepsis-induced cardiomyopathy, and thus controls apoptosis. Therefore, this review discusses melatonin as a promising drug for the management of sepsis-induced cardiomyopathy.

Roles of flavonoids in ischemic heart disease: Cardioprotective effects and mechanisms against myocardial ischemia and reperfusion injury

BACKGROUND

Flavonoids are extensively present in fruits, vegetables, grains, and medicinal plants. Myocardial ischemia and reperfusion (MI/R) comprise a sequence of detrimental incidents following myocardial ischemia. Research indicates that flavonoids have the potential to act as cardioprotective agents against MI/R injuries. Several specific flavonoids, e.g., luteolin, hesperidin, quercetin, kaempferol, and puerarin, have demonstrated cardioprotective activities in animal models.

PURPOSE

The objective of this review is to identify the cardioprotective flavonoids, investigate their mechanisms of action, and explore their application in myocardial ischemia.

METHODS

A search of PubMed database and Google Scholar was conducted using keywords "myocardial ischemia" and "flavonoids". Studies published within the last 10 years reporting on the cardioprotective effects of natural flavonoids on animal models were analyzed.

RESULTS

A total of 55 natural flavonoids were identified and discussed within this review. It can be summarized that flavonoids regulate the following main strategies: antioxidation, anti-inflammation, calcium modulation, mitochondrial protection, ER stress inhibition, anti-apoptosis, ferroptosis inhibition, autophagy modulation, and inhibition of adverse cardiac remodeling. Additionally, the number and position of OH, 3'4'-catechol, C2=C3, and C4=O may play a significant role in the cardioprotective activity of flavonoids.

CONCLUSION

This review serves as a reference for designing a daily diet to prevent or reduce damages following ischemia and screening of flavonoids for clinical application.

Activation of adenosine A2B receptor alleviates myocardial ischemia-reperfusion injury by inhibiting endoplasmic reticulum stress and restoring autophagy flux

Myocardial ischemia-reperfusion injury (MIRI) poses a significant threat to patients with coronary heart disease. Adenosine A2A receptors have been known as a protective role in MIRI by regulating autophagy, so we assumed that activation of adenosine A2B receptor (A2BAR) might exert a similar effect during MIRI and underlying mechanism be related to proteostasis maintenance as well. In situ hearts were subjected to 30 min of ischemia and 120 min of reperfusion (IR), while invitro cardiomyocytes from neonatal rats experienced 6 h of oxygen-glucose deprivation followed by 12 h of reoxygenation (OGDR). Initially, we observed that post-ischemia-reperfusion induced autophagy flux blockade and ERS both in vivo and in vitro, evident through the increased expression of p62, LC3II, and BIP, which indicated the deteriorated proteostasis. We used a selective A2BAR agonist, Bay 60-6583, to explore the positive effects of A2BAR on cardiomyocytes and found that A2BAR activation rescued damaged cardiac function and morphological changes in the IR group and improved frail cell viability in the OGDR group. The A2BAR agonist also alleviated the blockage of autophagic flux, coupled with augmented ERS in the IR/OGDR group, which was reassured by using an autophagy inhibitor chloroquine (CQ) and ERS inhibitor (4-PBA) in vitro. Additionally, considering cAMP/PKA as a well-known downstream effector of A2BAR, we utilized H89, a selective PKA inhibitor. We observed that the positive efficacy of Bay 60-6583 was inhibited by H89. Collectively, our findings demonstrate that the A2BAR/cAMP/PKA signaling pathway exerts a protective role in MIRI by mitigating impaired autophagic flux and excessive ERS.

Effects of grape seed-derived proanthocyanidin B2 pretreatment on oxidative stress, endoplasmic reticulum stress and apoptosis of renal tubular epithelial cells in renal ischemia-reperfusion injury model of mice

PURPOSE

To investigate the effect of grape seed-derived proanthocyanidin B2 (GSPB2) pretreatment on acute renal ischemia-reperfusion injury model of mice.

METHODS

50 mice were divided into 5 groups: Sham group: mice were treated with right nephrectomy. GSPB2 group: GSPB2 was injected intraperitoneally 45 min before right nephrectomy. IRI group: right kidney was resected and the left renal arteriovenous vessel was blocked for 45 min. GSPB2 + IRI group: GSPB2 was intraperitoneally injected 45 min before IRI established. GSPB2 + BRU + IRI group: GSPB2 and brusatol (BRU) were injected intraperitoneally 45 min before IRI established. Creatinine and urea nitrogen of mice were detected, and the kidney morphology and pathological changes of each group were detected by HE staining, PAS staining and transmission electron microscopy. Expressions of Nrf2, HO-1, GRP78, CHOP, and cleaved-caspase3 were detected by immunofluorescence staining and western blotting.

RESULTS

Morphology and mitochondrial damages of kidney in GSPB2 + IRI group were significantly alleviated than those in IRI group. Expression levels of Nrf2 and HO-1 were significantly higher in GSPB2 + IRI group than those in IRI group. Expression levels of GRP78, CHOP and cleaved-caspase3 were significantly lower in GSPB2 + IRI group than those in IRI group. However, compared to GSPB2 + IRI group, protective effects of GSPB2 pretreatment were weakened in GSPB2 + BRU + IRI group.

CONCLUSIONS

GSPB2 pretreatment could alleviate oxidative stress damage and reduce apoptosis of renal tubular epithelial cells, which might be related to activating the antioxidant system, up-regulating the expression of Nrf2 and HO-1, inhibiting the expressions of GRP78, CHOP and cleaved-caspase3. However, the protective effect could be reversed by brusatol.

Broadening horizons: The role of ferroptosis in myocardial ischemia-reperfusion injury

Ferroptosis is a novel type of regulated cell death (RCD) discovered in recent years, where abnormal intracellular iron accumulation leads to the onset of lipid peroxidation, which further leads to the disruption of intracellular redox homeostasis and triggers cell death. Iron accumulation with lipid peroxidation is considered a hallmark of ferroptosis that distinguishes it from other RCDs. Myocardial ischemia-reperfusion injury (MIRI) is a process of increased myocardial cell injury that occurs during coronary reperfusion after myocardial ischemia and is associated with high post-infarction mortality. Multiple experiments have shown that ferroptosis plays an important role in MIRI pathophysiology. This review systematically summarized the latest research progress on the mechanisms of ferroptosis. Then we report the possible link between the occurrence of MIRI and ferroptosis in cardiomyocytes. Finally, we discuss and analyze the related drugs that target ferroptosis to attenuate MIRI and its action targets, and point out the shortcomings of the current state of relevant research and possible future research directions. It is hoped to provide a new avenue for improving the prognosis of the acute coronary syndrome.

Xenon postconditioning attenuates neuronal injury after spinal cord ischemia/reperfusion injury by targeting endoplasmic reticulum stress-associated apoptosis

The purpose of the study is to explore the underlying mechanisms of xenon (Xe) which protects against spinal cord ischemia/reperfusion injury (SCIRI). A SCIRI rat model was induced by abdominal artery occlusion for 85 min and reperfusion. Xe postconditioning (50% Xe) was administered 1 h after 1 h of reperfusion. At reperfusion time points (2, 4, 6, and 24 h), rats were treated with spinal cord scans by MRI to assess the time of peak spinal cord injury after SCIRI. Subsequently, endoplasmic reticulum (ER) stress inhibitor sodium 4-phenylbutyrate (4-PBA) was administered by daily intraperitoneal injection (50 mg/kg) for 5 days before SCIRI. At 4 h after reperfusion, motor function, immunofluorescence staining, hematoxylin and eosin (HE) staining, Nissl staining, TUNEL staining, real-time reverse transcription polymerase chain (RT-PCR) reaction, and western blot analyses were performed to investigate the protective effects of Xe against SCIRI. In the rat I/R model, spinal cord edema peaked at reperfusion 4 h. SCIRI activated ER stress, which was located in neurons. Xe postconditioning remarkably alleviated hind limb motor function, reduced neuronal apoptosis rate, increased the number of normal neurons, and inhibited the expression of ER stress-related protein in spinal cord. Furthermore, the administration of the ER stress inhibitor 4-PBA strongly decreased ER stress-induced apoptosis following SCIRI. Xe postconditioning inhibits ER stress activation, which contributes to alleviate SCIRI by suppressing neuronal apoptosis.

LncRNAs and CircRNAs in Endoplasmic Reticulum Stress: A Promising Target for Cardiovascular Disease?

The endoplasmic reticulum (ER) is a principal subcellular organelle responsible for protein quality control in the secretory pathway, preventing protein misfolding and aggregation. Failure of protein quality control in the ER triggers several molecular mechanisms such as ER-associated degradation (ERAD), the unfolded protein response (UPR) or reticulophagy, which are activated upon ER stress (ERS) to re-establish protein homeostasis by transcriptionally and translationally regulated complex signalling pathways. However, maintenance over time of ERS leads to apoptosis if such stress cannot be alleviated. The presence of abnormal protein aggregates results in loss of cardiomyocyte protein homeostasis, which in turn results in several cardiovascular diseases such as dilated cardiomyopathy (DCM) or myocardial infarction (MI). The influence of a non-coding genome in the maintenance of proper cardiomyocyte homeostasis has been widely proven. To date, the impact of microRNAs in molecular mechanisms orchestrating ER stress response has been widely described. However, the role of long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) is just beginning to be addressed given the potential role of these RNA classes as therapeutic molecules. Here, we provide a current state-of-the-art review of the roles of distinct lncRNAs and circRNAs in the modulation of ERS and UPR and their impact in cardiovascular diseases.

Endoplasmic Reticulum Stress: A Key Regulator of Cardiovascular Disease

The problems associated with economic development and social progress have led to an increase in the occurrence of cardiovascular diseases (CVDs), which affect the health of an increasing number of people and are a leading cause of disease and population mortality worldwide. Endoplasmic reticulum stress (ERS), a hot topic of interest for scholars in recent years, has been confirmed in numerous studies to be an important pathogenetic basis for many metabolic diseases and play an important role in maintaining physiological processes. The endoplasmic reticulum (ER) is a major organelle that is involved in protein folding and modification synthesis, and ERS occurs when several physiological and pathological factors allow excessive amounts of unfolded/misfolded proteins to accumulate. ERS often leads to initiation of the unfolded protein response (UPR) in a bid to re-establish tissue homeostasis; however, UPR has been documented to induce vascular remodeling and cardiomyocyte damage under various pathological conditions, leading to or accelerating the development of CVDs such as hypertension, atherosclerosis, and heart failure. In this review, we summarize the latest knowledge gained concerning ERS in terms of cardiovascular system pathophysiology, and discuss the feasibility of targeting ERS as a novel therapeutic target for the treatment of CVDs. Investigation of ERS has immense potential as a new direction for future research involving lifestyle intervention, the use of existing drugs, and the development of novel drugs that target and inhibit ERS.

Mitophagy as a mitochondrial quality control mechanism in myocardial ischemic stress: from bench to bedside

Myocardial ischemia reduces the supply of oxygen and nutrients to cardiomyocytes, leading to an energetic crisis or cell death. Mitochondrial dysfunction is a decisive contributor to the reception, transmission, and modification of cardiac ischemic signals. Cells with damaged mitochondria exhibit impaired mitochondrial metabolism and increased vulnerability to death stimuli due to disrupted mitochondrial respiration, reactive oxygen species overproduction, mitochondrial calcium overload, and mitochondrial genomic damage. Various intracellular and extracellular stress signaling pathways converge on mitochondria, so dysfunctional mitochondria tend to convert from energetic hubs to apoptotic centers. To interrupt the stress signal transduction resulting from lethal mitochondrial damage, cells can activate mitophagy (mitochondria-specific autophagy), which selectively eliminates dysfunctional mitochondria to preserve mitochondrial quality control. Different pharmacological and non-pharmacological strategies have been designed to augment the protective properties of mitophagy and have been validated in basic animal experiments and pre-clinical human trials. In this review, we describe the process of mitophagy in cardiomyocytes under ischemic stress, along with its regulatory mechanisms and downstream effects. Then, we discuss promising therapeutic approaches to preserve mitochondrial homeostasis and protect the myocardium against ischemic damage by inducing mitophagy.

Arbutin abrogates testicular ischemia/reperfusion injury in rats through repression of inflammation and ER stress

The aim of this study was to investigate the effects of arbutin (ARB) administration on oxidative stress, inflammation, endoplasmic reticulum (ER) stress and apoptosis in an experimental testicular torsion/detorsion (T/D)-induced testicular injury model for the first time. A total of 24 male Sprague-Dawley rats were divided into four groups with six rats in each group: sham control, T/D, T/D+ARB (50 mg/kg) and T/D+ARB (100 mg/kg). Torsion and detorsion times were applied as 4 h and 2 h, respectively. The levels of lipid peroxidation [malondialdehyde (MDA)] and oxidative stress [total oxidant status (TOS) and total antioxidant status (TAS)] in testicular tissues were determined using colorimetric methods. The levels of DNA damage [8-hydroxy-2'-deoxyguanosine (8-OHdG)], antioxidant system [superoxide dismutase (SOD) and catalase (CAT)], pro-inflammatory cytokines [high mobility group box 1 (HMGB1), nuclear factor kappa B protein 65 (NF-κB p65), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and myeloperoxidase (MPO)], ER stress [78-kDa glucose-regulated protein (GRP78), activating transcription factor 6 (ATF6) and CCAAT-enhancer-binding protein homologous protein (CHOP)] and apoptosis (caspase-3) markers in testicular tissues were determined using commercial enzyme-linked immunosorbent assay (ELISA) kits. Johnsen's testicle scoring system was used for histological evaluation. In the T/D group, it was determined that statistically significant increasing in the levels of oxidative stress, inflammation, ER stress and apoptosis compared with sham control group (p < 0.05). ARB administrations statistically significantly restored testicular I/R damage in a dose dependent manner (p < 0.05). In addition, it was determined that the data of histological examinations supported the biochemical results. Our findings support the hypothesis that ARB may be used as a protective agent against T/D-induced testicular damage.

Cardioplegia in Open Heart Surgery: Age Matters

INTRODUCTION

Cardioplegia is a pharmacological approach essential for the protection of the heart from ischemia-reperfusion (I-R) injury. Over the years, numerous cardioplegic solutions have been developed, with each cardioplegic approach having its advantages and disadvantages. Cardioplegic solutions can be divided into crystalloid and blood cardioplegic solutions, and an experienced surgeon chooses the type of solution based on the individual needs of patients in order to provide optimal heart protection. Importantly, the pediatric immature myocardium is structurally, physiologically, and metabolically different from the adult heart, and consequently its needs to achieve cardioplegic arrest strongly differ. Therefore, the present review aimed to provide a summary of the cardioplegic solutions available to pediatric patients with a special focus on emphasizing differences in heart injury after various cardioplegic solutions, the dosing strategies, and regimens.

MATERIAL AND METHODS

The PubMed database was searched using the terms cardioplegia, I-R, and pediatric population, and studies that investigated the influence of cardioplegic strategies on markers of cardiac muscle damage were further analyzed in this review.

CONCLUSIONS

A large body of evidence suggested more prominent benefits achieved with blood compared to those with crystalloid cardioplegia in pediatric myocardium preservation. However, standardized and uniform protocols have not been established so far, and an experienced surgeon chooses the type of cardioplegia solution based on the individual needs of patients, while the severity of myocardial damage strongly depends on the type and duration of the surgical procedure, overall patient condition, and presence of comorbidities, etc.

Insights into research on myocardial ischemia/reperfusion injury from 2012 to 2021: a bibliometric analysis

BACKGROUND

Numerous studies on myocardial ischemia/reperfusion (MI/R) injury have been undertaken in recent years. Hotspots and developmental trends in MI/R research are being rapidly updated. However, there has been no bibliometric analysis that systematically evaluates existing literature on MI/R injury. Our study explores developments in MI/R research over the past decade, and provides a reference for future research.

MATERIALS AND METHODS

Both experimental and clinical publications on MI/R injury from 2012 to 2021 were retrieved from the Web of Science Core Collection database. The CiteSpace and VOSviewer tools were used to perform a bibliometric analysis.

RESULTS

A total of 8419 papers were analyzed. The number of annual publications demonstrated an overall upward trend, rising from 629 publications in 2012 to 1024 publications in 2021. China, the USA, Germany, England, and Italy were the top five contributors to MI/R studies. The Fourth Military Medical University in China contributed the most publications (188, 2.23%), while the University College London in England cooperated the most with relevant research institutions. Derek J Hausenloy (University College London), Derek M Yellon (University College London), and Gerd Heusch (University of Essen Medical School) were the top three most active and influential scholars according to the H-index. Among the top 10 journals with the most publications, Basic Research in Cardiology had the highest impact factors. The top three co-cited journals were Circulation, Circulation Research, and Cardiovascular Research. According to a co-cited reference analysis, MI/R research can be divided across 10 major subfields of mitophagy, cardioprotection, inflammation, remote ischemic preconditioning, long non-coding RNA, melatonin, postconditioning, mitochondria, microvascular obstruction, and ferroptosis. After 2018, the keywords with strongest citation bursts included extracellular vesicles, long non-coding RNA, cell proliferation, microRNA, mitochondrial quality control, mitophagy, biomarker, and mitochondrial biogenesis.

CONCLUSIONS

The present study reveals the influential authors, cooperating institutions, and main research foci in the field of MI/R injury in the past decade. The latest hotspots are a more in-depth insight into the molecular mechanisms underlying MI/R injury, such as mitochondrial quality control, non-coding RNAs, cell proliferation, and extracellular vesicles.

Replication of standard bovine viral diarrhea strain OregonC24Va induces endoplasmic reticulum stress-mediated apoptosis of bovine trophoblast cells

Bovine viral diarrhea (BVD) is a worldwide infectious disease caused by bovine viral diarrhea virus (BVDV) infection, which invades the placenta, causes abortion, produces immune tolerance and continuously infects calves, and causes huge economic losses to the cattle industry. The endoplasmic reticulum (ER) is an important organelle in cells, which is prone to ER stress after being stimulated by pathogens, thus activating the ER stress-related apoptosis. Studies have confirmed that BVDV can utilize the ER of its host to complete its own proliferation and stimulate ER stress to a certain extent. However, the role of ER stress in BVDV infecting bovine placental trophoblast cells (BTCs) and inducing apoptosis is still unclear. We are using the cytopathic strain of BVDV (OregonC24Va), which can cause apoptosis of BTCs, as a model system to determine how ER stress induced by BVDV affects placental toxicity. We show that OregonC24Va can infect BTCs and proliferate in it. With the proliferation of BVDV in BTCs, ER stress-related apoptosis is triggered. The ER stress inhibitor 4-PBA was used to inhibit the ER stress of BTCs, which not only inhibited the proliferation of BVDV, but also reduced the apoptosis of BTCs. The ER stress activator Tg can activate ER stress-related apoptosis, but the proliferation of BVDV does not change in BTCs. Therefore, BVDV utilizes the UPR of activated ER stress to promote the proliferation of BVDV in the early stage of infection, and activates the ER stress-related apoptosis of BTCs in the later stage with the virus proliferation to promote the cell apoptosis and further spread of the virus. Our research provides a new theoretical basis for exploring the placental infection and vertical transmission of BVDV.

Impact of myeloid differentiation protein 1 on cardiovascular disease

Cardiovascular disease remains the leading cause of disability and mortality worldwide and a significant global burden. Many lines of evidence suggest complex remodeling responses to cardiovascular disease, such as myocardial ischemia, hypertension and valve disease, which lead to poor clinical outcomes, including heart failure, arrhythmia and sudden cardiac death (SCD). The mechanisms underlying cardiac remodeling are closely related to reactive oxygen species (ROS) and inflammation. Myeloid differentiation protein 1 (MD1) is a secreted glycoprotein known as lymphocyte antigen 86. The complex of MD1 and radioprotective 105 (RP105) is an important regulator of inflammation and is involved in the modulation of vascular remodeling and atherosclerotic plaque development. A recent study suggested that the expression of MD1 in hypertrophic cardiomyopathy (HCM) patients is decreased compared with that in donor hearts. Therefore, MD1 may play an important role in the pathological processes of cardiovascular disease and have potential clinical value. Here, this review aims to discuss the current knowledge regarding the role of MD1 in the regulation of cardiac pathophysiology.

Transmembrane BAX inhibitor motif containing 6 suppresses presenilin-2 to preserve mitochondrial integrity after myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion (I/R) damage is characterized by mitochondrial damage in cardiomyocytes. Transmembrane BAX inhibitor motif containing 6 (TMBIM6) and presenilin-2 (PS2) participate in multiple mitochondrial pathways; thus, we investigated the impact of these proteins on mitochondrial homeostasis during an acute reperfusion injury. Myocardial post-ischemic reperfusion stress impaired myocardial function, induced structural abnormalities and promoted cardiomyocyte death by disrupting the mitochondrial integrity in wild-type mice, but not in TMBIM6 transgenic mice. We found that TMBIM6 bound directly to PS2 and promoted its post-transcriptional degradation. Knocking out PS2 in mice reduced I/R injury-induced cardiac dysfunction, inflammatory responses, myocardial swelling and cardiomyocyte death by improving the mitochondrial integrity. These findings demonstrate that sufficient TMBIM6 expression can prevent PS2 accumulation during cardiac I/R injury, thus suppressing reperfusion-induced mitochondrial damage. Therefore, TMBIM6 and PS2 are promising therapeutic targets for the treatment of cardiac reperfusion damage.

SGLT2i reduces renal injury by improving mitochondrial metabolism and biogenesis

OBJECTIVES

Despite advances in treatment, an effective therapeutic strategy for acute kidney injury (AKI) is still lacking. Considering the widely reported clinical benefits of canagliflozin in the kidneys, we assessed the effects of canagliflozin on AKI.

METHODS

Lipopolysaccharide was used to induce AKI in the presence of canagliflozin.

RESULTS

Canagliflozin treatment reduced blood urea nitrogen and serum creatinine levels and improved the renal tubular structure in mice with lipopolysaccharide-induced septic AKI. Canagliflozin also suppressed the inflammatory response, oxidative stress and tubular cell death in the kidneys during septic AKI. In vitro, canagliflozin supplementation maintained mitochondrial function in lipopolysaccharide-treated HK-2 cells by restoring the mitochondrial membrane potential, inhibiting mitochondrial reactive oxygen species production and normalizing mitochondrial respiratory complex activity. In HK-2 cells, canagliflozin stimulated the adenosine monophosphate-activated protein kinase catalytic subunit alpha 1 (AMPKα1)/peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α)/nuclear respiratory factor 1 (NRF1) pathway, thus elevating the number of live and healthy mitochondria following lipopolysaccharide treatment. Inhibition of the AMPKα1/PGC1α/NRF1/mitochondrial biogenesis pathway abolished the protective effects of canagliflozin on renal cell mitochondria and tubular viability. Similarly, the protective effects of canagliflozin on kidney function and tubular structure were abrogated in AMPKα1-knockout mice.

CONCLUSIONS

Canagliflozin could be used to treat septic AKI by activating the AMPKα1/PGC1α/NRF1/mitochondrial biogenesis pathway.

ERK/HIF-1α/VEGF pathway: a molecular target of ELABELA (ELA) peptide for attenuating cardiac ischemia-reperfusion injury in rats by promoting angiogenesis

BACKGROUND

Myocardial ischemia-reperfusion (I/R) injury is caused by a chain of events such as endothelial dysfunction. This study was conducted to investigate protective effects of ELABELA against myocardial I/R in Wistar rats and clarify its possible mechanisms. METHODS AND RESULTS: MI model was established based on the left anterior descending coronary artery ligation for 30 min. Then, 5 µg/kg of ELA peptide was intraperitoneally infused in rats once per day for 4 days. Western blot assay was used to assay the expression of t-ERK1/2, and p-ERK1/2 in different groups. The amount of myocardial capillary density, the expression levels of VEGF and HIF-1α were evaluated using immunohistochemistry assay. Masson's trichrome staining was utilized to assay cardiac interstitial fibrosis. The results showed that establishment of MI significantly enhanced cardiac interstitial fibrosis and changed p-ERK1/2/ t-ERK1/2 ratio. Likewise, ELA post-treatment markedly increased myocardial capillary density, the expression of several angiogenic factors (VEGF-A, HIF-1α), and reduced cardiac interstitial fibrosis by activation of ERK1/2 signaling pathways.

CONCLUSION

Collectively, ELA peptide has ability to reduce myocardial I/R injury by promoting angiogenesis and reducing cardiac interstitial fibrosis through activating ERK/HIF-1α/VEGF pathway.

Endoplasmic Reticulum Stress-Related Signature for Predicting Prognosis and Immune Features in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) with cancer cells under endoplasmic reticulum (ER) stress has a poor prognosis. This study is aimed at discovering credible biomarkers for predicting the prognosis of HCC based on ER stress-related genes (ERSRGs). We constructed a novel four-ERSRG prognostic risk model, including PON1, AGR2, SSR2, and TMCC1, through a series of bioinformatic approaches, which can accurately predict survival outcomes in HCC patients. Higher risk scores were linked to later grade, recurrence, advanced TNM stage, later T stage, and HBV infection. In addition, 20 fresh frozen tumors and normal tissues from HCC patients were collected and used to validate the genes expressed in the signature by qRT-PCR and immunohistochemical (IHC) assays. Moreover, we found the ER stress-related signature could reflect the infiltration levels of different immune cells in the tumor microenvironment (TME) and forecast the efficacy of immune checkpoint inhibitor (ICI) treatment. Finally, we created a nomogram incorporating this ER stress-related signature. In conclusion, our constructed four-gene risk model associated with ER stress can accurately predict survival outcomes in HCC patients, and the model's risk score is associated with the poor clinical classification.

Preclinical multi-target strategies for myocardial ischemia-reperfusion injury

Despite promising breakthroughs in diagnosing and treating acute coronary syndromes, cardiovascular disease’s high global mortality rate remains indisputable. Nearly half of these patients died of ischemic heart disease. Primary percutaneous coronary intervention (PCI) and coronary artery bypass grafting can rapidly restore interrupted blood flow and become the most effective method for salvaging viable myocardium. However, restoring blood flow could increase the risk of other complications and myocardial cell death attributed to myocardial ischemia-reperfusion injury (IRI). How to reduce the damage of blood reperfusion to ischemic myocardium has become an urgent problem to be solved. In preclinical experiments, many treatments have substantial cardioprotective effects against myocardial IRI. However, the transition from these cardioprotective therapies to clinically beneficial therapies for patients with acute myocardial infarction remains elusive. The reasons for the failure of the clinical translation may be multi-faceted, and three points are summarized here: (1) Our understanding of the complex pathophysiological mechanisms of myocardial IRI is far from enough, and the classification of specific therapeutic targets is not rigorous, and not clear enough; (2) Most of the clinical patients have comorbidities, and single cardioprotective strategies including ischemia regulation strategies cannot exert their due cardioprotective effects under conditions of hyperglycemia, hypertension, hyperlipidemia, and aging; (3) Most preclinical experimental results are based on adult, healthy animal models. However, most clinical patients had comorbidities and received multiple drug treatments before reperfusion therapy. In 2019, COST Action proposed a multi-target drug combination initiative for prospective myocardial IRI; the optimal cardioprotective strategy may be a combination of additive or synergistic multi-target therapy, which we support. By establishing more reasonable preclinical models, screening multi-target drug combinations more in line with clinical practice will benefit the translation of clinical treatment strategies.

Mitochondrial quality control in diabetic cardiomyopathy: from molecular mechanisms to therapeutic strategies

In diabetic cardiomyopathy (DCM), a major diabetic complication, the myocardium is structurally and functionally altered without evidence of coronary artery disease, hypertension or valvular disease. Although numerous anti-diabetic drugs have been applied clinically, specific medicines to prevent DCM progression are unavailable, so the prognosis of DCM remains poor. Mitochondrial ATP production maintains the energetic requirements of cardiomyocytes, whereas mitochondrial dysfunction can induce or aggravate DCM by promoting oxidative stress, dysregulated calcium homeostasis, metabolic reprogramming, abnormal intracellular signaling and mitochondrial apoptosis in cardiomyocytes. In response to mitochondrial dysfunction, the mitochondrial quality control (MQC) system (including mitochondrial fission, fusion, and mitophagy) is activated to repair damaged mitochondria. Physiological mitochondrial fission fragments the network to isolate damaged mitochondria. Mitophagy then allows dysfunctional mitochondria to be engulfed by autophagosomes and degraded in lysosomes. However, abnormal MQC results in excessive mitochondrial fission, impaired mitochondrial fusion and delayed mitophagy, causing fragmented mitochondria to accumulate in cardiomyocytes. In this review, we summarize the molecular mechanisms of MQC and discuss how pathological MQC contributes to DCM development. We then present promising therapeutic approaches to improve MQC and prevent DCM progression.

Chlorogenic acid ameliorates torsion/detorsion-induced testicular injury via decreasing endoplasmic reticulum stress

BACKROUND

Testicular torsion (TT) is an urological emergency situation especially in adolescents and young men. The main pathophysiology of testicular torsion/detorsion (T/D) is ischemia-reperfusion (I/R) injury. I/R induces the production of reactive oxygen species (ROS) thought to play a critical role in tissue injury. Increasing evidence suggests that ER stress may play an important role in I/R-induced cell death. During ischemia, oxygen and glucose deprivation also causes abnormalities in protein folding processes. Antioxidants suppress oxidative stress directly as well as ER stress and thus gain importance in the treatment of pathologies associated with oxidative stress and ER stress, such as I/R damage. Chlorogenic acid (CGA) which is formed by the esterification of caffeic and quinic acids and is one of the most abundant phenolic acids in nature. There is also a growing body of studies reporting protective effects of CGA against I/R injury in different tissues, including intestinal, heart and brain.

OBJECTIVE

To investigate the effects of CGA on oxidative stress and ER stress in an experimental testicular I/R injury model.

DESIGN

Rats were divided into three groups: control, T/D, and T/D + CGA. In the T/D + CGA group, 100 mg/kg CGA was given intraperitoneally 30 min before detorsion. While tissue malondialdehyde (MDA) levels were determined manually using a colorimetric method, tissue superoxide dismutase (SOD), 78-kDa glucose regulatory protein (GRP78), activating transcription factor 6 (ATF6) and C/EBP homologous protein (CHOP) levels were determined enzyme-linked immunosorbent assay (ELISA) kits. Johnsen's testicle scoring system was used for histological evaluation.

RESULTS

In T/D group, tissue MDA, GRP78, ATF6 and CHOP levels were significantly higher than control group (p < 0.05). These increases were significantly reversed with CGA pre-treatment (p < 0.05). The histopathological Johnsen score was significantly lower in the T/D group compared to the control group, but the level of histopathological Johnsen score was significantly restored by CGA pre-treatment (p < 0.05).

DISCUSSION

The relationship between I/R injury and ER stress has been emphasized frequently in recent years. This study in which the effects of CGA on TT were examined for the first time, showed that CGA can inhibit I/R-induced testicular damage.

CONCLUSION

These results may provide a new insight into CGA and may form the first clinical theoretical basis for the possible use of CGA in the treatment of TT in the future. However, the real function of CGA in TT patients needs further investigation.

Inhibition of Myocardial Cell Apoptosis Is Important Mechanism for Ginsenoside in the Limitation of Myocardial Ischemia/Reperfusion Injury

Ischemic heart disease has a high mortality, and the recommended therapy is reperfusion. Nevertheless, the restoration of blood flow to ischemic tissue leads to further damage, namely, myocardial ischemia/reperfusion injury (MIRI). Apoptosis is an essential pathogenic factor in MIRI, and ginsenosides are effective in inhibiting apoptosis and alleviating MIRI. Here, we reviewed published studies on the anti-apoptotic effects of ginsenosides and their mechanisms of action in improving MIRI. Each ginsenoside can regulate multiple pathways to protect the myocardium. Overall, the involved apoptotic pathways include the death receptor signaling pathway, mitochondria signaling pathway, PI3K/Akt signaling pathway, NF-κB signaling pathway, and MAPK signaling pathway. Ginsenosides, with diverse chemical structures, regulate different apoptotic pathways to relieve MIRI. Summarizing the effects and mechanisms of ginsenosides contributes to further mechanism research studies and structure-function relationship research studies, which can help the development of new drugs. Therefore, we expect that this review will highlight the importance of ginsenosides in improving MIRI via anti-apoptosis and provide references and suggestions for further research in this field.

Targeting IRE1α-JNK-c-Jun/AP-1-sEH Signaling Pathway Improves Myocardial and Coronary Endothelial Function Following Global Myocardial Ischemia/Reperfusion

Objectives: Endoplasmic reticulum (ER) stress and soluble epoxide hydrolase (sEH) upregulation/activation have been implicated in myocardial ischemia/reperfusion (I/R) injury. We previously reported that ER stress mediates angiotensin II-induced sEH upregulation in coronary endothelium, whether and how ER stress regulates sEH expression to affect postischemic cardiac function remain unexplored. This study aimed to unravel the signaling linkage between ER stress and sEH in an ex vivo model of myocardial I/R injury. Methods: Hearts from male Wistar-Kyoto rats were mounted on a Langendorff apparatus and randomly allocated to 7 groups, including control, I/R (30-min ischemia and 60-min reperfusion), and I/R groups pretreated with one of the following inhibitors: 4-PBA (targeting: ER stress), GSK2850163 (IRE1α), SP600125 (JNK), SR11302 (AP-1), and DCU (sEH). The inhibitor was administered for 15 min before ischemia with a peristaltic pump. Hemodynamic parameters including left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), and maximal velocity of contraction (+dp/dt_max) and relaxation (-dp/dt_max) of the left ventricle were continuously recorded using an intraventricular balloon. Endothelial dilator function of the left anterior descending artery was studied in a wire myograph upon completion of reperfusion. The expression of ER stress molecules, JNK, c-Jun, and sEH was determined by western-blot. Results: I/R decreased LVSP (105.5±6.4 vs. 146.9±13.4 mmHg), and increased LVEDP (71.4±3.0 vs. 6.0±2.7 mmHg), with a resultant decreased LVDP (34.1±9.2 vs. 140.9±13.1 mmHg). I/R attenuated +dp/dt_max (651.7±142.1 vs. 2806.6±480.6 mmHg/s) and -dp/dt_max (-580.0±109.6 vs. -2118.0±244.9 mmHg/s) (all ps<0.001). The I/R-induced cardiac dysfunction could be alleviated by 4-PBA (LVSP 119.5±15.6 mmHg, p<0.01; LVEDP 21.2±4.2 mmHg, LVDP 98.3±12.0 mmHg, +dp/dt_max 2166.7±208.4 mmHg/s, and -dp/dt_max -1350.9±99.8 mmHg/s, all ps<0.001), GSK2850163 (LVSP 113.4±10.9 mmHg, p<0.01; LVEDP 37.1±3.1 mmHg, LVDP 76.3±13.9 mmHg, +dp/dt_max 1586.5±263.3 mmHg/s, -dp/dt_max -1127.7±159.9 mmHg/s, all ps<0.001), SP600125 (LVSP 113.9±5.6 mmHg, LVDP 40.5±3.3 mmHg, +dp/dt_max 970.1±89.8 mmHg/s, all ps<0.01), SR11302 (LVSP 97.9±7.5 mmHg, p<0.01; LVEDP 52.7±8.6mmHg, p<0.001; LVDP 45.2±9.8mmHg, p<0.05; +dp/dt_max 1231.5±196.6 mmHg/s, p<0.01; -dp/dt_max -658.3±68.9 mmHg/s, p<0.05), or DCU (LVSP 109.9±4.1 mmHg, p<0.01; LVEDP 11.7±1.8 mmHg, LVDP 98.2±4.9 mmHg, +dp/dt_max 1869.8±121.9 mmHg/s, and -dp/dt_max -1492.3±30.8 mmHg/s, all ps<0.001). The relaxant response of the coronary artery to acetylcholine was decreased after I/R in terms of both magnitude and sensitivity (p<0.001). All inhibitors improved acetylcholine-induced relaxation. Global I/R increased sEH expression and induced ER stress in both myocardium and coronary artery. Inhibition of ER stress or IRE1α downregulated I/R-induced sEH expression and inhibited JNK and c-Jun phosphorylation. Both JNK and AP-1 inhibitors lowered sEH level in myocardium and coronary artery in I/R-injured hearts. Conclusions: This study deciphered the molecular linkage between ER stress and sEH regulation in global I/R insult by uncovering a novel signaling axis of IRE1α-JNK-c-Jun/AP-1-sEH, which provided basis for future research on the therapeutic potential of targeting the IRE1α-JNK-c-Jun/AP-1-sEH axis for ischemic myocardial injury.

The Cell Protective Effect of Adenine on Hypoxia-Reoxygenation Injury through PPAR Delta Activation

Ischemia followed by blood supply reperfusion in cardiomyocytes leads to an overproduction of free radicals and a rapid decrease of adenosine triphosphate concentration. The cardioprotective effect of a potential drug, adenine, was evaluated using H9c2 rat cardiomyoblasts. After hypoxia–reoxygenation (HR) treatment consisting of hypoxia for 21 h followed by reoxygenation for 6 h, it was revealed that pretreatment with 200 µM adenine for 2 h effectively prevented HR-induced cell death. Adenine also significantly decreased the production of reactive oxygen species and reduced cell apoptosis after HR injury. The antioxidant effect of adenine was also revealed in this study. Adenine pretreatment significantly reduced the expression of activating transcription factor 4 (ATF4) and glucose-regulated protein 78 (GRP78) proteins, and protein disulfide isomerase induced a protective effect on mitochondria after HR stimulation. Intracellular adenosine monophosphate-activated protein kinase, peroxisome proliferator-activated receptor delta (PPARδ), and perilipin levels were increased by adenine after HR stimulation. Adenine had a protective effect in HR-damaged H9c2 cells. It may be used in multiple preventive medicines in the future.

BI-1 ameliorates myocardial injury by activating the mitochondrial unfolded protein response and FUNDC1-related mitophagy in cardiorenal syndrome type 3

It has been suggested that mitochondrial dysfunction underlies the myocardial injury seen following cardiorenal syndrome type 3 (CRS-3). Both mitophagy and the mitochondrial unfolded protein response (UPR^mt) are protective programs that preserve mitochondrial homeostasis. Here, we explored whether Bax inhibitor-1 (BI-1) overexpression attenuates CRS-3-related myocardial injury through activation of mitophagy and the UPR^mt in cardiomyocytes. Following CRS-3 induction via renal ischemia-reperfusion injury, BI-1 transgenic (BI1^TG) mice showed greater preservation of myocardial integrity and relaxation function and less cardiomyocyte apoptosis than wild-type (WT) mice. Moreover, BI-1 overexpression attenuated CRS-3-mediated myocardial inflammation, as indicated by decreased MCP-1 and IL-6 expression and normalized ATP production in cardiomyocytes. After CRS-3 induction, mitophagy was inhibited in cardiomyocytes from WT mice, as indicated by both decreased Fundc1 transcription and mt-Keima fluorescence, and modest activation of the UPR^mt, denoted by a slight increase in Atf6 mRNA levels. By contrast, activation of mitophagy and marked UPR^mt upregulation were observed in cardiac tissue from BI1^TG mice. shRNA-mediated silencing of Fundc1 or Atf6 greatly impaired mitochondrial metabolism and survival in cultured cardiomyocytes overexpressing BI-1. Thus, upregulation of BI-1 expression aimed at activating mitophagy and the UPR^mt may represent a useful therapeutic approach for the treatment of CRS-3.

Inhibition of MALT1 Alleviates Spinal Ischemia/Reperfusion Injury-Induced Neuroinflammation by Modulating Glial Endoplasmic Reticulum Stress in Rats

PURPOSE

Glial activation and the disorders of cytokine secretion induced by endoplasmic reticulum stress (ERS) are crucial pathogenic processes in establishing ischemia/reperfusion (I/R) injury of the brain and spinal cord. This present study aimed to investigate the effects of mucous-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) on spinal cord ischemia/reperfusion (SCI/R) injury via regulating glial ERS.

METHODS

SCI/R was induced by thoracic aorta occlusion-reperfusion in rats. The MALT1-specific inhibitor MI-2 or human recombinant MALT1 protein (hrMALT1) was administrated for three consecutive days after the surgery. Immunofluorescent staining was used to detect the localization of MALT1 and ERS profiles in activated astrocyte and microglia of spinal cord. The ultrastructure of endoplasmic reticulum (ER) was examined by transmission electron microscopy. Blood-spinal cord barrier (BSCB) disruption and noninflammatory status were assessed. The neuron loss and demyelination in the spinal cord were monitored, and the hindlimb motor function was evaluated in SCI/R rats.

RESULTS

Intraperitoneally postoperative MI-2 treatment down-regulated phos-NF-κB (p65) and Bip (ERS marker protein) expression in the spinal cord after SCI/R in rats. Intraperitoneal injection MI-2 attenuated the swelling/dilation of ER of the glia in SCI/R rats. Furthermore, MI-2 attenuated I/R-induced Evans blue (EB) leakage and microglia M1 polarization in spinal cord, implying a role for MALT1 in the BSCB destruction and neuroinflammation after SCI/R in rats. Furthermore, intrathecal injection of hrMALT1 aggravated the fragmentation of neuron, loss of neurofibrils and demyelination caused by I/R, while 4-PBA, an ERS inhibitor, co-treatment with hrMALT1 reversed these effects in SCI/R rats. hrMALT1 administration aggravated the motor deficit index (MDI) scoring, while 4-PBA co-treatment improved SCI/R-induced motor deficits in rats.

CONCLUSION

Inhibition of MALT1 alleviates SCI/R injury-induced neuroinflammation by modulating glial endoplasmic reticulum stress in rats.

MKP-1 Overexpression Reduces Postischemic Myocardial Damage through Attenuation of ER Stress and Mitochondrial Damage

Mitochondrial dysfunction and endoplasmic reticulum (ER) stress contribute to postischemic myocardial damage, but the upstream regulatory mechanisms have not been identified. In this study, we analyzed the role of mitogen-activated protein kinase (MAPK) phosphatase 1 (MKP-1) in the regulation of mitochondrial function and ER stress in hypoxic cardiomyocytes. Our results show that MKP-1 overexpression sustains viability and reduces hypoxia-induced apoptosis among H9C2 cardiomyocytes. MKP-1 overexpression attenuates ER stress and expression of ER stress genes and improves mitochondrial function in hypoxia-treated H9C2 cells. MKP-1 overexpression also increases ATP production and mitochondrial respiration and attenuates mitochondrial oxidative damage in hypoxic cardiomyocytes. Moreover, our results demonstrate that ERK and JNK are the downstream signaling targets of MKP-1 and that MKP-1 overexpression activates ERK, while it inhibits JNK. Inhibition of ERK reduces the ability of MKP-1 to preserve mitochondrial function and ER homeostasis in hypoxic cardiomyocytes. These results show that MKP-1 plays an essential role in the regulation of mitochondrial function and ER stress in hypoxic H9C2 cardiomyocytes through normalization of the ERK pathway and suggest that MKP-1 may serve as a novel target for the treatment of postischemic myocardial injury.

Abnormal Mitochondria-Endoplasmic Reticulum Communication Promotes Myocardial Infarction

Myocardial infarction is characterized by cardiomyocyte death, and can be exacerbated by mitochondrial damage and endoplasmic reticulum injury. In the present study, we investigated whether communication between mitochondria and the endoplasmic reticulum contributes to cardiomyocyte death after myocardial infarction. Our data demonstrated that hypoxia treatment (mimicking myocardial infarction) promoted cardiomyocyte death by inducing the c-Jun N-terminal kinase (JNK) pathway. The activation of JNK under hypoxic conditions was dependent on overproduction of mitochondrial reactive oxygen species (mtROS) in cardiomyocytes, and mitochondrial division was identified as the upstream inducer of mtROS overproduction. Silencing mitochondrial division activators, such as B cell receptor associated protein 31 (BAP31) and mitochondrial fission 1 (Fis1), repressed mitochondrial division, thereby inhibiting mtROS overproduction and preventing JNK-induced cardiomyocyte death under hypoxic conditions. These data revealed that a novel death-inducing mechanism involving the BAP31/Fis1/mtROS/JNK axis promotes hypoxia-induced cardiomyocyte damage. Considering that BAP31 is localized within the endoplasmic reticulum and Fis1 is localized in mitochondria, abnormal mitochondria-endoplasmic reticulum communication may be a useful therapeutic target after myocardial infarction.

Mitofusin-2 Enhances Mitochondrial Contact With the Endoplasmic Reticulum and Promotes Diabetic Cardiomyopathy

Diabetic cardiomyopathy has been associated with mitochondrial damage. Mitochondria–endoplasmic reticulum (ER) contact is an important determinant of mitochondrial function and ER homeostasis. We therefore investigated whether hyperglycemia can damage the mitochondria by increasing their contact with the ER in cardiomyocytes. We found that hyperglycemia induced mitochondria–ER contact in cardiomyocytes, as evidenced by the increased MMM1, MDM34, and BAP31 expressions. Interestingly, the silencing of Mfn2 reduced the cooperation between the mitochondria and the ER in cardiomyocytes. Mfn2 silencing improved cardiomyocyte viability and function under hyperglycemic conditions. Additionally, the silencing of Mfn2 markedly attenuated the release of calcium from the ER to the mitochondria, thereby preserving mitochondrial metabolism in cardiomyocytes under hyperglycemic conditions. Mfn2 silencing reduced mitochondrial reactive oxygen species production, which reduced mitochondria-dependent apoptosis in hyperglycemia-treated cardiomyocytes. Finally, Mfn2 silencing attenuated ER stress in cardiomyocytes subjected to high-glucose stress. These results demonstrate that Mfn2 promotes mitochondria–ER contact in hyperglycemia-treated cardiomyocytes. The silencing of Mfn2 sustained mitochondrial function, suppressed mitochondrial calcium overload, prevented mitochondrial apoptosis, and reduced ER stress, thereby enhancing cardiomyocyte survival under hyperglycemic conditions.

Endoplasmic reticulum stress promotes epithelial‑mesenchymal transition via the PERK signaling pathway in paraquat‑induced pulmonary fibrosis

Pulmonary fibrosis is the primary reason for mortality in patients with paraquat (PQ) poisoning. Our previous study demonstrated that epithelial-mesenchymal transition (EMT) had a role in PQ-induced pulmonary fibrosis. However, the role of endoplasmic reticulum (ER) stress in PQ-induced EMT remains clear. The present study aimed to determine the role of ER stress in EMT in PQ-induced pulmonary fibrosis. A549 and RLE-6TN cells were incubated with LY294002 (a PI3K inhibitor) or transfected with protein kinase RNA-like ER kinase (PERK) small interfering RNA (si) for 24 h prior to being exposed to PQ. Next, the expression levels of ER stress-related proteins, PI3K/AKT/GSK-3β signaling pathway-related proteins and EMT-related markers were analyzed by performing western blotting, reverse transcription-quantitative PCR and immunofluorescence assays. The results of the present study revealed that the protein expression levels of PERK, phosphorylated (p)-PERK, p-eukaryotic initiation factor 2 (eIF2)α were significantly upregulated in the PQ group, whereas p-PI3K, p-AKT and p-GSK-3β were significantly upregulated in the sicontrol + PQ group compared with the sicontrol group. In vitro, following transfection with siPERK or treatment with the PI3K inhibitor, the protein expression levels of E-cadherin (an epithelial marker) were upregulated, whereas the protein expression levels of α-SMA (a mesenchymal marker) were downregulated. Immunofluorescence analysis revealed that the levels of E-cadherin were markedly upregulated, whereas the levels of α-SMA were notably downregulated following transfection with siPERK compared with the sicontrol group. The results of wound healing assay demonstrated that cell migration in the siPERK + PQ group was markedly decreased compared with the sicontrol + PQ group. These indicated that PQ-induced EMT was suppressed after silencing PERK. The expression levels of p-GSK-3β, p-AKT and p-PI3K were also markedly downregulated in the siPERK + PQ group compared with the sicontrol + PQ group. In conclusion, the findings of the present study suggested that ER stress may promote EMT through the PERK signaling pathway in PQ-induced pulmonary fibrosis. Thus, ER stress may represent a potential therapeutic target for PQ-induced pulmonary fibrosis.