Dexmedetomidine Attenuates Myocardial Ischemia-Reperfusion Injury in Diabetes Mellitus by Inhibiting Endoplasmic Reticulum Stress

Anshen Shumai Decoction inhibits post-infarction inflammation and myocardial remodeling through suppression of the p38 MAPK/c-FOS/EGR1 pathway

Anshen Shumai Decoction (ASSMD) is traditionally employed to manage coronary artery disease arrhythmias. Its protective efficacy against myocardial infarction remains to be elucidated. This investigation employed a rat model of myocardial infarction, achieved through the ligation of the left anterior descending (LAD) coronary artery, followed by a 28-day administration of ASSMD. The study observed the decoction's mitigative impact on myocardial injury, with gene regulation effects discerned through transcriptomic analysis. Furthermore, ASSMD's influence on cardiomyocyte apoptosis and fibrotic protein secretion was assessed using an embryonic rat cardiomyocyte cell line (H9c2) under hypoxic conditions and rat cardiac fibroblasts subjected to normoxic culture conditions with TGF-β. A functional rescue assay involving overexpression of FOS and Early Growth Response Factor 1 (EGR1), combined with inhibition of the p38 Mitogen-activated Protein Kinase (MAPK) pathway, was conducted. Results indicated that ASSMD significantly curtailed cardiomyocyte apoptosis and myocardial fibrosis in infarcted rats, primarily by downregulating FOS and EGR1 gene expression and inhibiting the upstream p38 MAPK pathway. These actions of ASSMD culminated in reduced expression of pro-apoptotic, collagen, and fibrosis-associated proteins, conferring myocardial protection and anti-fibrotic effects on cardiac fibroblasts.

Insight into Cardioprotective Effects and Mechanisms of Dexmedetomidine

PURPOSE

Cardiovascular disease remains the leading cause of death worldwide. Dexmedetomidine is a highly selective α2 adrenergic receptor agonist with sedative, analgesic, anxiolytic, and sympatholytic properties, and several studies have shown its possible protective effects in cardiac injury. The aim of this review is to further elucidate the underlying cardioprotective mechanisms of dexmedetomidine, thus suggesting its potential in the clinical management of cardiac injury.

RESULTS AND CONCLUSION

Our review summarizes the findings related to the involvement of dexmedetomidine in cardiac injury and discusses the results in the light of different mechanisms. We found that numerous mechanisms may contribute to the cardioprotective effects of dexmedetomidine, including the regulation of programmed cell death, autophagy and fibrosis, alleviation of inflammatory response, endothelial dysfunction and microcirculatory derangements, improvement of mitochondrial dysregulation, hemodynamics, and arrhythmias. Dexmedetomidine may play a promising and beneficial role in the treatment of cardiovascular disease.

Characterization of the m6A regulators' landscape highlights the clinical significance of acute myocardial infarction

Objective

Acute myocardial infarction (AMI) is a severe cardiovascular disease that threatens human life and health globally. N6-methyladenosine (m6A) governs the fate of RNAs via m6A regulators. Nevertheless, how m6A regulators affect AMI remains to be deciphered. To solve this issue, an integrative analysis of m6A regulators in AMI was conducted.

Methods

We acquired transcriptome profiles (GSE59867, GSE48060) of peripheral blood samples from AMI patients and healthy controls. Key m6A regulators were used for LASSO, and consensus clustering was conducted. Next, the m6A score was also computed. Immune cell infiltration, ferroptosis, and oxidative stress were evaluated. In-vitro and in-vivo experiments were conducted to verify the role of the m6A regulator ALKBH5 in AMI.

Results

Most m6A regulators presented notable expression alterations in circulating cells of AMI patients versus those of controls. Based on key m6A regulators, we established a gene signature and a nomogram for AMI diagnosis and risk prediction. AMI patients were classified into three m6A clusters or gene clusters, respectively, and each cluster possessed the unique properties of m6A modification, immune cell infiltration, ferroptosis, and oxidative stress. Finally, the m6A score was utilized to quantify m6A modification patterns. Therapeutic targeting of ALKBH5 greatly alleviated apoptosis and intracellular ROS in H/R-induced H9C2 cells and NRCMs.

Conclusion

Altogether, our findings highlight the clinical significance of m6A regulators in the diagnosis and risk prediction of AMI and indicate the critical roles of m6A modification in the regulation of immune cell infiltration, ferroptosis, and oxidative stress.

Dexmedetomidine as a cardioprotective drug: a narrative review

Dexmedetomidine (DEX), a highly selective alpha2-adrenoceptors agonist, is not only a sedative drug used during mechanical ventilation in the intensive care unit but also a cardio-protective drug against ischemia-reperfusion injury (IRI). Numerous preclinical in vivo and ex vivo studies, mostly evaluating the effect of DEX pretreatment in healthy rodents, have shown the efficacy of DEX in protecting the hearts from IRI. However, whether DEX can maintain its cardio-protective effect in hearts with comorbidities such as diabetes has not been fully elucidated. Multiple clinical trials have reported promising results, showing that pretreatment with DEX can attenuate cardiac damage in patients undergoing cardiac surgery. However, evidence of the post-treatment effects of DEX in clinical practice remains limited. In this narrative review, we summarize the previously reported evidence of DEX-induced cardio-protection against IRI and clarify the condition of the hearts and the timing of DEX administration that has not been tested. With further investigations evaluating these knowledge gaps, the use of DEX as a cardio-protective drug could be further facilitated in the management of patients undergoing cardiac surgery and might be considered in a broader area of clinical settings beyond cardiac surgery, including patients with acute myocardial infarction.

Linderalactone mitigates diabetic cardiomyopathy in mice via suppressing the MAPK/ATF6 pathway

Diabetic cardiomyopathy (DCM) is a challenging diabetic complication that manifests as chronic inflammation. Yet, the mechanism underlying diabetes-associated myocardial injury is not fully understood. We investigated the pharmacological effects and mechanisms of linderalactone, a natural compound that can prevent diabetes-induced cardiomyopathy in mice. Diabetes was induced by a single dose of streptozotocin (120 mg/kg, i.p.). Diabetic mice were administrated with linderalactone (2.5 or 5 mg/kg) by gavage for five weeks. Harvested heart tissues were then subjected to RNA-sequencing analysis to explore the potential mechanism of linderalactone. Linderalactone prevented heart dysfunction by inhibiting myocardial hypertrophy, fibrosis, and inflammation, without altering blood glucose. RNA-sequencing indicated that linderalactone exerted its cardioprotective effects mainly by affecting the mitogen-activated protein kinase (MAPK)/ activating transcription factor 6 (ATF6) pathway. Linderalactone also suppressed endoplasmic reticulum (ER) stress mediated by the diabetes-activated MAPKs/ATF6 pathway, thereby reducing myocardial hypertrophy and inflammation in heart tissues and in cultured cardiomyocytes. Inhibition of MAPKs or a deficiency of ATF6 in cardiomyocytes mimicked the linderalactone-associated decreases in high glucose-induced hypertrophy and inflammation. Linderalactone showed beneficial effects in alleviating diabetic cardiomyopathy, in part by modulating the MAPK/ATF6 signaling pathway to mitigate myocardial hypertrophy and inflammation. Linderalactone may have clinical utility in the treatment for diabetes-associated cardiomyopathy.

Dexmedetomidine attenuates hepatic ischemia-reperfusion injury-induced apoptosis via reducing oxidative stress and endoplasmic reticulum stress

Dexmedetomidine (DEX) affords a hepatoprotective effect during ischemia-reperfusion (IR) injury (IRI); however, the underlying mechanism remains elusive. In this work, using a rat liver IR model and a BRL-3A cell hypoxia-reoxygenation (HR) model, we explored whether DEX protects the liver against IRI by decreasing oxidative stress (OS), endoplasmic reticulum stress (ERS), and apoptotic pathways. We found that DEX significantly increased SOD and GSH activity while decreasing ROS and MDA levels in BRL-3A cells, successfully preventing HR-induced OS damage. DEX administration reduced JNK, ERK, and P38 phosphorylation and blocked HR-induced MAPK signaling pathway activation. Additionally, DEX administration reduced the expression of GRP78, IRE1α, XBP1, TRAF2, and CHOP, which reduced HR-induced ERS. NAC prevented the MAPK pathway from being activated and inhibited the ERS pathway. Further research showed that DEX significantly reduced HR-induced apoptosis by suppressing the expression of Bax/Bcl-2 and cleaved caspase-3. Similarly, animal studies demonstrated DEX exerted a protective effect of the liver by alleviating histopathological injury and enhancing liver function, mechanically DEX reduced cell apoptosis in liver tissue by reducing oxidative stress and ERS. In conclusion, DEX mitigates OS and ERS during IR, thereby suppressing cell apoptosis, thus providing protection to the liver.

Integrated chemical profiling, network pharmacology and pharmacological evaluation to explore the potential mechanism of Xinbao pill against myocardial ischaemia-reperfusion injury

CONTEXT

Xinbao pill (XBW), a traditional Chinese herbal formula, is widely used in clinical treatment for cardiovascular diseases; however, the therapeutic effect of XBW on myocardial ischaemia-reperfusion injury (MI/RI) is unclear.

OBJECTIVE

This study evaluates the cardioprotective effect and molecular mechanism of XBW against MI/RI.

MATERIALS AND METHODS

A phytochemistry-based network pharmacology analysis was used to uncover the mechanism of XBW against MI/RI. Ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method was used to identify chemicals. MI/RI-related targets of XBW were predicted using TargetNet database, OMIC database, etc. Sprague-Dawley (SD) rats under anterior descending artery ligation model were divided into Sham, MI/RI and XBW (180 mg/kg, intragastric administration). After 30 min ischaemia and 24 h reperfusion, heart tissues were collected for measurement of myocardial infarct size. After oxygen glucose deprivation for 6 h, H9c2 cells were treated with XBW (60, 240 and 720 μg/mL) and diazoxide (100 μM) for 18 h of reperfusion.

RESULTS

Thirty-seven chemicals were identified in XBW; 50 MI/RI-related targets of XBW were predicted using indicated databases. XBW significantly reduced infarct size and creatine kinase MB (CK-MB) level after MI/RI; XBW protected H9c2 cells against OGD/R injury. Gene ontology (GO) and KEGG pathway enrichment analyses by String database showed that the cardioprotective effect of XBW was associated with autophagy and apoptosis signalling pathways. Experimental investigation also verified that XBW suppressed apoptosis, autophagy and endoplasmic reticulum (ER) stress.

CONCLUSIONS

XBW showed therapeutic effects against MI/RI mainly via attenuating apoptosis though suppressing excessive autophagy and ER stress.

Targeted activation of ERK1/2 reduces ischemia and reperfusion injury in hyperglycemic myocardium by improving mitochondrial function

Background

Diabetes can increase the risk of coronary heart disease, and also increase the mortality rate of coronary heart disease in diabetic patients. Although reperfusion therapy can preserve the viable myocardium, fatal reperfusion injury can also occur. Studies have shown that diabetes can aggravate myocardial ischemia-reperfusion injury, ERK1/2 can reduce myocardial ischemia-reperfusion injury, but its mechanism in hyperglycemic myocardial ischemia-reperfusion injury is unclear. This study sought to explore the mechanism of extracellular signal-regulated kinase 1/2 (ERK1/2) in hyperglycemic myocardial ischemia reperfusion (I/R) injury.

Methods

H9C2 cardiomyocytes were treated with high-glucose (HG) medium plus I/R stimulation to establish a hyperglycemia I/R model in vitro. The cells were treated with LM22B-10 (an ERK activator) or transfected with the constitutive activation of the mitogen-activated protein kinase 1 (CaMEK) gene. Myocardial cell apoptosis, mitochondria functional-related indicators, the oxidative stress indexes, and the expression levels of ERK1/2 protein were detected.

Results

The HG I/R injury intervention caused an increase in the ratio of apoptotic cardiomyocytes (P<0.05), but the phosphorylation level of the ERK1/2 protein did not increase further. Administering LM22B-10 or transfecting the CaMEK gene significantly activated the phosphorylation levels of ERK1/2 protein and reduced the proportion of cardiomyocyte apoptosis (P<0.05). HG I/R injury increased mitochondrial fission and reduced membrane potential. The intervention reduced the number of punctate mitochondria, increased the average network structure size and median branch length (P<0.01), increased the median network structure size and average branch length (P<0.05), and reduced the colocalization of Drp1 (Dynamin-Related protein1)/TOMM20 (Mitochondrial outer membrane translocation enzyme 20) (P<0.05) and Drp1 with serine 616 phosphorylation (Drp1s616) phosphorylation (P<0.01), thereby reducing mitochondrial fission, increasing membrane potential and mitochondrial function. HG I/R injury increased the level of oxidative stress, while administering LM22B-10 or transfecting the CaMEK gene reduced the level of oxidative stress (P<0.01).

Conclusions

Targeting the activation of ERK1/2 protein phosphorylation reduced mitochondrial fission, increased membrane potential and mitochondrial function, reduced oxidative stress and myocardial cell apoptosis, and alleviated hyperglycemia myocardial I/R injury.

Amelioration of myocardial ischemia/reperfusion injury in diabetes: A narrative review of the mechanisms and clinical applications of dexmedetomidine

Mechanisms contributing to the pathogenesis of myocardial ischemia-reperfusion (I/R) injury are complex and multifactorial. Many strategies have been developed to ameliorate myocardial I/R injuries based on these mechanisms. However, the cardioprotective effects of these strategies appear to diminish in diabetic states. Diabetes weakens myocardial responses to therapies by disrupting intracellular signaling pathways which may be responsible for enhancing cellular resistance to damage. Intriguingly, it was found that Dexmedetomidine (DEX), a potent and selective α2-adrenergic agonist, appears to have the property to reverse diabetes-related inhibition of most intervention-mediated myocardial protection and exert a protective effect. Several mechanisms were revealed to be involved in DEX’s protection in diabetic rodent myocardial I/R models, including PI3K/Akt and associated GSK-3β pathway stimulation, endoplasmic reticulum stress (ERS) alleviation, and apoptosis inhibition. In addition, DEX could attenuate diabetic myocardial I/R injury by up-regulating autophagy, reducing ROS production, and inhibiting the inflammatory response through HMGB1 pathways. The regulation of autonomic nervous function also appeared to be involved in the protective mechanisms of DEX. In the present review, the evidence and underlying mechanisms of DEX in ameliorating myocardial I/R injury in diabetes are summarized, and the potential of DEX for the treatment/prevention of myocardial I/R injury in diabetic patients is discussed.

LncRNA UCA1 epigenetically suppresses APAF1 expression to mediate the protective effect of sevoflurane against myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MI/RI) is a leading cause of death globally. Whereas some long noncoding RNAs (lncRNAs) are known to participate in the progression of MI/RI, the role of urothelial carcinoma associated 1 (UCA1) in conjunction with sevoflurane treatment remains largely unknown. H9C2 cardiomyocytes were subjected to hypoxia/reoxygenation (H/R) to establish an in vitro MI/RI model, and sevoflurane was then added. Cell viability, apoptosis, SOD activity, and MDA levels were measured. Levels of inflammatory cytokines and methylation of apoptosis protease-activating factor 1 (APAF1) were determined. Interactions among lncRNA UCA1, enhancer of zeste homologue 2 (EZH2), DNA methyltransferase-1 (DNMT1), and APAF1 were analyzed. After H/R treatment, the viability of H9C2 cardiomyocytes decreased and apoptosis rate, oxidative stress factor levels, inflammatory cytokine levels, and apoptosis-related protein levels all increased. Sevoflurane treatment reversed these changes. LncRNA UCA1 knockdown attenuated the therapeutic effect of sevoflurane on H/R-treated cardiomyocytes, and silencing of APAF1 reversed this role of UCA1 knockdown. Moreover, lncRNA UCA1 recruited DNMT1 through EZH2, thus promoting methylation of the APAF1 promoter region. LncRNA UCA1 recruits DNMT1 to promote methylation of the APAF1 promoter through EZH2, thus strengthening the protective effect of sevoflurane on H/R-induced cardiomyocyte injury.

Dexmedetomidine exerts its protective effect on cerebral ischemia reperfusion injury in mice by inhibiting ferroptosis

OBJECTIVES

Stroke is one of the major diseases that can threaten human life and health. The incidence of ischemic stroke accounts for more than 70% of stroke. The mechanism of ischemia reperfusion (IR) injury caused by ischemic stroke is extremely complex. In recent years, dexmedetomidine has been increasingly studied in anti-cerebral IR injury as a common clinical anesthetic adjunct, but its specific mechanism is not fully understood. Therefore, this study aims to explore the effects and mechanisms of dexmedetomidine on cerebral IR injury in mice.

METHODS

The mouse middle cerebral artery occlusion (MCAO) model was prepared by modified suture method. Male ICR mice were randomly divided into a sham group, an IR group, an IR+D1 group (IR+administered 25 µg/kg dexmedetomidine), an IR+D2 group(IR+administered 50 µg/kg dexmedetomidine), an IR+D3 group (IR+administered 100 µg/kg dexmedetomidine), and an IR+D2+ML385 group (IR+administered 50 µg/kg dexmedetomidine and 30 mg/kg ML385). The neurologic behavior of mice was evaluated by Longa's five-point method. 2,3,5-triphenyltetrazolium chloride (TTC) staining was used to detect the percentage of cerebral infarct volume in mice. The protein expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), transferrin receptor 1 (TFR1), glutathione peroxidase 4 (GPX4), and solute carrier family 7 member 11 (SLC7A11) in the cerebral tissues of mice were detected by Western blotting.Mitochondrial morphology was observed under the transmission electron microscope. The contents of MDA, Fe2+, and GSH in the cerebral tissues of mice were detected.

RESULTS

Compared with the sham group, neurobehavioral scores, cerebral infarct volume, the contents of MDA and Fe2+, as well as the protein expression of TFR1 were significantly increased; the contents of GSH and the protein expression of SLC7A11 and GPX4 were significantly reduced (all P<0.05); mitochondria in cerebral tissue were wrinkled, cristae were reduced, and membrane density was increased in the IR group. Compared with the IR group, neurobehavioral scores, cerebral infarction volume, MDA and Fe2+ contents, as well as the protein expression of TFR1 were significantly reduced; the contents of GSH and the protein expression of SLC7A11 and GPX4 were significantly increased (all P<0.05); mitochondrial damage in cerebral tissue was significantly relieved with the pre-treatment of dexmedetomidine. Compared with the IR+D2 group, neurobehavioral scores, cerebral infarction volume, MDA and Fe2+ contents, as well as the protein expression of TFR1 were significantly increased; the contents of GSH and the protein expression of SLC7A11 and GPX4 were significantly reduced (all P<0.05);mitochondria reappeared significantly damaged with the ML385 on the basis of dexmedetomidine pre-treatment.

CONCLUSIONS

The protective effect of dexmedetomidine on cerebral IR injury mice is related to its inhibition of ferroptosis, and the mechanism might be related to its regulation of Nrf2 expression.

Propofol postconditioning alleviates diabetic myocardial ischemia‑reperfusion injury via the miR‑200c‑3p/AdipoR2/STAT3 signaling pathway

Myocardial ischemia/reperfusion (MI/RI) syndrome is one of the leading causes of mortality and disability. Propofol postconditioning is known to improve myocardial ischemia/reperfusion injury (MI/RI). The present study aimed to explore the mechanism of propofol postconditioning in diabetic MI/RI. Diabetic MI/RI rat models were established and the rats were treated via propofol postconditioning. Staining with 2,3,5-triphenyl-2H-tetrazolium chloride, H&E staining, TUNEL staining and ELISA were applied to detect infarct size, pathological changes, apoptosis and oxidative stress-related factor and apoptotic factor levels, respectively. Subsequently, the effect of propofol on H9C2 cells was also assessed using the Cell Counting Kit-8 assay. High-glucose hypoxia/reperfusion (H/R) models of H9C2 cardiomyocytes were established. miR-200c-3p overexpression or AdipoR2 silencing combined with propofol postconditioning was performed in H/R-induced H9C2 cells and STAT3 protein expression levels were determined. Propofol postconditioning significantly reduced myocardial infarct size, oxidative stress and apoptosis in diabetic MI/RI models. Furthermore, propofol postconditioning significantly reduced the oxidative stress and apoptosis of H9C2 cells in high-glucose H/R models. Propofol postconditioning also significantly downregulated miR-200c-3p expression levels and promoted AdipoR2 expression levels. miR-200c-3p overexpression or AdipoR2 downregulation significantly reversed the effects of propofol postconditioning on its antioxidation and anti-apoptotic effects in H9C2 cells and on decreasing STAT3 phosphorylation levels. Together, the results of the present study demonstrated that propofol postconditioning inhibited miR-200c-3p, upregulated AdipoR2 and activated the STAT3 signaling pathway, thus alleviating diabetic MI/RI and therefore highlighting its potential as a treatment of diabetic MI/RI.

Recent Advances in the Clinical Value and Potential of Dexmedetomidine

Dexmedetomidine, a highly selective α2-adrenoceptor agonist, has sedative, anxiolytic, analgesic, sympatholytic, and opioid-sparing properties and induces a unique sedative response which shows an easy transition from sleep to wakefulness, thus allowing a patient to be cooperative and communicative when stimulated. Recent studies indicate several emerging clinical applications via different routes. We review recent data on dexmedetomidine studies, particularly exploring the varying routes of administration, experimental implications, clinical effects, and comparative advantages over other drugs. A search was conducted on the PubMed and Web of Science libraries for recent studies using different combinations of the words “dexmedetomidine”, “route of administration”, and pharmacological effect. The current routes, pharmacological effects, and application categories of dexmedetomidine are presented. It functions by stimulating pre- and post-synaptic α2-adrenoreceptors within the central nervous system, leading to hyperpolarization of noradrenergic neurons, induction of an inhibitory feedback loop, and reduction of norepinephrine secretion, causing a sympatholytic effect, in addition to its anti-inflammation, sleep induction, bowel recovery, and sore throat reduction effects. Compared with similar α2-adrenoceptor agonists, dexmedetomidine has both pharmacodynamics advantage of a significantly greater α2:α1-adrenoceptor affinity ratio and a pharmacokinetic advantage of having a significantly shorter elimination half-life. In its clinical application, dexmedetomidine has been reported to present a significant number of benefits including safe sedation for various surgical interventions, improvement of intraoperative and postoperative analgesia, sedation for compromised airways without respiratory depression, nephroprotection and stability of hypotensive hemodynamics, reduction of postoperative nausea and vomiting and postoperative shivering incidence, and decrease of intraoperative blood loss. Although the clinical application of dexmedetomidine is promising, it is still limited and further research is required to enhance understanding of its pharmacological properties, patient selection, dosage, and adverse effects.

Knockdown of XIST up-regulates 263294miR-340-5p to relieve myocardial ischaemia-reperfusion injury via inhibiting cyclin D1

Aim

Long non‐coding RNAs (lncRNAs) are known to participate in various human diseases, while the role of X inactive‐specific transcript (XIST) binding microRNA‐340‐5p (miR‐340‐5p) remains seldom studied. We aim to identify the role of the XIST/miR‐340‐5p/cyclin D1 (CCND1) axis in the myocardial ischaemia–reperfusion injury (MIRI).

Methods and results

The mouse MIRI models were established. The expression of XIST, miR‐340‐5p, and CCND1 in mouse myocardial tissues in MIRI mice was assessed. The MIRI mice were respectively treated with altered XIST, miR‐340‐5p, or CCND1. The changes of myocardial enzyme activity were assessed, and the cardiac function was evaluated. Myocardial pathological changes, cardiomyocyte apoptosis and related apoptotic factors, oxidative stress and inflammatory factors were observed in myocardial tissues in mice with MIRI. The binding relationships between XIST and miR‐340‐5p, and between miR‐340‐5p and CCND1 were confirmed. XIST and CCND1 were up‐regulated while miR‐340‐5p was down‐regulated in MIRI mice. Silenced XIST could elevated miR‐340‐5p expression and reduced CCND1 expression, so as to promoted cardiac function and suppressed myocardial enzyme activity, ameliorated pathological changes, decelerated cardiomyocyte apoptosis by elevating Bcl‐2 but reducing the levels of Bax and Caspase‐3, attenuated inflammatory response by repressing IL‐6 and TNF‐α levels, and mitigated oxidative stress by reducing MDA contents and increasing CAT, GSH‐Px, and SOD levels in MIRI mice. XIST sponged miR‐340‐5p and miR‐340‐5p targeted CCND1.

Conclusions

Knockdown of XIST up‐regulates miR‐340‐5p to relieve MIRI via inhibiting CCND1.

A Novel Insight Into the Fate of Cardiomyocytes in Ischemia-Reperfusion Injury: From Iron Metabolism to Ferroptosis

Ischemia-reperfusion injury (IRI), critically involved in the pathology of reperfusion therapy for myocardial infarction, is closely related to oxidative stress the inflammatory response, and disturbances in energy metabolism. Emerging evidence shows that metabolic imbalances of iron participate in the pathophysiological process of cardiomyocyte IRI [also termed as myocardial ischemia-reperfusion injury (MIRI)]. Iron is an essential mineral required for vital physiological functions, including cellular respiration, lipid and oxygen metabolism, and protein synthesis. Nevertheless, cardiomyocyte homeostasis and viability are inclined to be jeopardized by iron-induced toxicity under pathological conditions, which is defined as ferroptosis. Upon the occurrence of IRI, excessive iron is transported into cells that drive cardiomyocytes more vulnerable to ferroptosis by the accumulation of reactive oxygen species (ROS) through Fenton reaction and Haber–Weiss reaction. The increased ROS production in ferroptosis correspondingly leads cardiomyocytes to become more sensitive to oxidative stress under the exposure of excess iron. Therefore, ferroptosis might play an important role in the pathogenic progression of MIRI, and precisely targeting ferroptosis mechanisms may be a promising therapeutic option to revert myocardial remodeling. Notably, targeting inhibitors are expected to prevent MIRI deterioration by suppressing cardiomyocyte ferroptosis. Here, we review the pathophysiological alterations from iron homeostasis to ferroptosis together with potential pathways regarding ferroptosis secondary to cardiovascular IRI. We also provide a comprehensive analysis of ferroptosis inhibitors and initiators, as well as regulatory genes involved in the setting of MIRI.

Knockdown of lncRNA Abhd11os attenuates myocardial ischemia/reperfusion injury by inhibiting apoptosis in cardiomyocytes

ABSTRACT

Long non-coding RNA (lncRNA) is one potential target for the treatment of various disorders. Here, we explored the role of Abhd11os in ischemia/reperfusion-induced myocardial injury, and preliminarily explored the regulatory mechanisms. Relative Abhd11os expression level was examined by qRT-PCR. Western blot was done to measure the expression of apoptotic-related proteins. CCK-8 assay and flow cytometry were performed to detect cell viability and apoptosis, respectively. ELISA assay was used to ensure the levels of LDH, CK, and cTnI in serum. Besides, the infarct sizes were confirmed by TTC and Evans blue staining. Apoptotic rate of cardiomyocytes in myocardial tissues was evaluated by TUNEL assay. Here, increased Abhd11os expression was found in rat myocardial ischemia/reperfusion injury (MIRI) model and hypoxia/reoxygenation (H/R)-treated cardiomyocytes. Subsequently, our data in vitro showed that upregulation of Abhd11os inhibited proliferation of cardiomyocytes, but promoted cell apoptosis. In animal experiments, myocardial infarct size in MIRI rats was reduced by Abhd11os knockdown. Moreover, downregulation of Abhd11os inhibited apoptosis of cardiomyocytes. Overall, our results revealed that knockdown of Abhd11os could notably attenuate H/R-induced myocardial injury through suppressing apoptosis of cardiomyocytes. These data suggest that Abhd11os may be a potential target for MIRI therapy.

Dexmedetomidine Protects Human Cardiomyocytes Against Ischemia-Reperfusion Injury Through α2-Adrenergic Receptor/AMPK-Dependent Autophagy

Background: Ischemia-reperfusion injury (I/R) strongly affects the prognosis of children with complicated congenital heart diseases (CHDs) who undergo long-term cardiac surgical processes. Recently, the α2-adrenergic receptor agonist Dexmedetomidine (Dex) has been reported to protect cardiomyocytes (CMs) from I/R in cellular models and adult rodent models. However, whether and how Dex may protect human CMs in young children remains largely unknown. Methods and Results: Human ventricular tissue from tetralogy of Fallot (TOF) patients and CMs derived from human-induced pluripotent stem cells (iPSC-CMs) were used to assess whether and how Dex protects human CMs from I/R. The results showed that when pretreated with Dex, the apoptosis marker-TUNEL and cleaved caspase 3 in the ventricular tissue were significantly reduced. In addition, the autophagy marker LC3II was significantly increased compared with that of the control group. When exposed to the hypoxia/reoxygenation process, iPSC-CMs pretreated with Dex also showed reduced TUNEL and cleaved caspase 3 and increased LC3II. When the autophagy inhibitor (3-methyladenine, 3-MA) was applied to the iPSC-CMs, the protective effect of Dex on the CMs was largely blocked. In addition, when the fusion of autophagosomes with lysosomes was blocked by Bafilomycin A1, the degradation of p62 induced by Dex during the autophagy process was suspended. Moreover, when pretreated with Dex, both the human ventricle and the iPSC-CMs expressed more AMP-activated protein kinase (AMPK) and phospho AMPK (pAMPK) during the I/R process. After AMPK knockout or the use of an α2-adrenergic receptor antagonist-yohimbine, the protection of Dex and its enhancement of autophagy were inhibited. Conclusion: Dex protects young human CMs from I/R injury, and α2-adrenergic receptor/AMPK-dependent autophagy plays an important role during this process. Dex may have a therapeutic effect for children with CHD who undergo long-term cardiac surgical processes.

Advanced research on the regulated necrosis mechanism in myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury is an important factor that seriously affects the prognosis of patients with myocardial infarction. It can cause myocardial stun, no-reflow phenomenon, reperfusion arrhythmia, and even irreversible cardiomyocyte death. Regulated necrosis is a newly discovered type of regulatory cell death that is different from apoptosis, including necroptosis, pyrolysis, iron death and other forms. Regulated necrosis plays an important role in myocardial infarction, heart failure and other cardiovascular diseases, as well as myocardial ischemia-reperfusion injury and other pathophysiological processes, and is expected to become a new target for intervention in this type of disease.

Dexmedetomidine Attenuates Ischemia/Reperfusion-Induced Myocardial Inflammation and Apoptosis Through Inhibiting Endoplasmic Reticulum Stress Signaling

Background

Endoplasmic reticulum stress (ERS)-mediated myocardial inflammation and apoptosis plays an important role in myocardial ischemia/reperfusion (I/R) injury. Dexmedetomidine has been used clinically with sedative, analgesic, and anti-inflammatory properties. This study aimed to determine the effects of dexmedetomidine pretreatment on inflammation, apoptosis, and the expression of ERS signaling during myocardial I/R injury.

Methods

Rats underwent myocardial ischemia for 30 min and reperfusion for 6 h, and H9c2 cardiomyocytes were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) injury (OGD for 12 h and reoxygenation for 3 h). Dexmedetomidine was administered prior to myocardial ischemia in rats or ODG in cardiomyocytes. In addition, the α2-adrenergic receptor antagonist (yohimbine) or the PERK activator (CCT020312) was given prior to dexmedetomidine treatment.

Results

Dexmedetomidine pretreatment decreased serum levels of cardiac troponin I, reduced myocardial infarct size, alleviated histological structure damage, and improved left ventricular function following myocardial I/R injury in rats. In addition, dexmedetomidine pretreatment increased cell viability and reduced cytotoxicity following OGD/R injury in cardiomyocytes. Mechanistically, the cardioprotection offered by dexmedetomidine was mediated via the inhibition of inflammation and apoptosis through downregulating the expression of the ERS signaling pathway, including glucose-regulated protein 78 (GRP78), protein kinase R-like endoplasmic reticulum kinase (PERK), C/EBP homologous protein (CHOP), inositol-requiring protein 1 (IRE1), and activating transcription factor 6 (ATF6). Conversely, the protective effects of dexmedetomidine were diminished by blocking the α2 adrenergic receptors with yohimbine or promoting PERK phosphorylation with CCT020312.

Conclusion

Dexmedetomidine pretreatment protects the hearts against I/R injury via inhibiting inflammation and apoptosis through downregulation of the ERS signaling pathway. Future clinical studies are needed to confirm the cardioprotective effects of dexmedetomidine in patients at risk of myocardial I/R injury.

Dexmedetomidine alleviates myocardial ischemia/reperfusion-induced injury and Ca2+ overload via the microRNA-346-3p/CaMKIId axis

Myocardial ischemia/reperfusion (MI/R) may impair cardiac functions. Dexmedetomidine (DEX) is protective in various clinical cases. Therefore, this study investigated the role and mechanism of DEX in MI/R. The myocardial infarct size, apoptosis, and levels of myocardial enzymes, SOD, ROS, Ca²⁺, and inflammatory factors in DEX-treated MI/R rats were measured. Differentially expressed microRNAs (miRs) in DEX-treated MI/R rats were detected. miR-346-3p was intervened to assess the effects of DEX on MI/R rats. The targeted binding relationship between miR-346-3p and CaMKIId was predicted and verified. DEX effect on hypoxia/reoxygenation (H/R)-induced cell model was evaluated. The role of CaMKIId in DEX protection was assessed after CaMKIId overexpression in H/R cells. NF-κB pathway and NLRP3 inflammasome-related protein levels were detected. DEX alleviated the myocardial injury and Ca²⁺ overload in MI/R rats, as evidenced by reduced infarct size, apoptosis and levels of myocardial enzymes, ROS, Ca²⁺, and inflammatory factors. DEX promoted miR-346-3p expression in MI/R rats, and miR-346-3p knockdown reversed DEX protection on MI/R rats. miR-346-3p targeted CaMKIId. DEX improved H/R-induced cell injury and Ca²⁺ overload and inhibited NF-κB/NLRP3 inflammasome-related protein levels, which were all reversed by CaMKIId overexpression. DEX alleviated injury and Ca²⁺ overload in MI/R via regulating the miR-346-3p/CaMKIId axis and inhibiting the NF-κB/NLRP3 inflammasome pathway.

Prominent and emerging anti-diabetic molecular targets

Diabetes is on the rise across the globe affecting more than 463 million people and crucially increasing morbidities of diabetes-associated diseases. Urgent and immense actions are needed to improve diabetes prevention and treatment. Regarding the correlation of diabetes with many associated diseases, inhibition of the disease progression is more crucial than controlling symptoms. Currently, anti-diabetic drugs are accompanied by undesirable side-effects and target confined types of biomolecules. Thus, extensive research is demanding to identify novel disease mechanisms and molecular targets as probable candidates for effective treatment of diabetes. This review discusses the conventional molecule targets that have been applied for their therapeutic rationale in treatment of diabetes. Further, the emerging and prospective molecular targets for the future focus of library screenings are presented.

Dexmedetomidine at a dose of 1 µM attenuates H9c2 cardiomyocyte injury under 3 h of hypoxia exposure and 3 h of reoxygenation through the inhibition of endoplasmic reticulum stress

Myocardial ischemia-reperfusion injury (MIRI) has been confirmed to induce endoplasmic reticulum stress (ERS) during downstream cascade reactions after the sufficient deterioration of cardiomyocyte function. However, clinically outcomes have been inconsistent with experimental findings because the mechanism has not been entirely elucidated. Dexmedetomidine (DEX), an α² adrenergic receptor agonist with anti-inflammatory and organ-protective activity, has been shown to attenuate IRI in the heart. The present study aimed to determine whether DEX is able to protect injured cardiomyocytes under in vitro hypoxia/reoxygenation (H/R) conditions and evaluate the conditions under which ERS is efficiently ameliorated. The cytotoxicity of DEX in H9c2 cells was evaluated 24 h after treatment with several different concentrations of DEX. The most appropriate H/R model parameters were determined by the assessment of cell viability and injury with Cell Counting Kit-8 and lactate dehydrogenase (LDH) release assays after incubation under hypoxic conditions for 3 h and reoxygenation conditions for 3, 6, 12 and 24 h. Additionally, the aforementioned methods were used to assess cardiomyocytes cultured with various concentrations of DEX under H/R conditions. Furthermore, the degree of apoptosis and the mRNA and protein expression levels of glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP) and caspase-12 were evaluated in all groups. The addition of 1, 5 and 10 µM DEX to the cell culture significantly increased the proliferation of H9c2 cells by >80% under normal culture conditions. In the H/R model assessment, following 3 h of anoxia exposure, H9c2 cell viability decreased to 62.67% with 3 h of reoxygenation and to 36% with 6 h of reoxygenation compared with the control. The viability of H9c2 cells subjected to hypoxia for 3 h and reoxygenation for 3 h increased by 61.3% when pretreated with 1 µM DEX, and the LDH concentration in the supernatant was effectively decreased by 13.7%. H/R significantly increased the percentage of apoptotic cells, as detected by flow cytometry, and increased the expression levels of GRP78, CHOP and caspase-12, while treatment with either DEX or 4-phenylbutyric acid (4-PBA) significantly attenuated these effects. Additionally, despite the protective effect of DEX against H/R injury, 4-PBA attenuated the changes induced by DEX and H/R. In conclusion, treatment with 1 µM DEX alleviated cell injury, apoptosis and the increases in GRP78, CHOP and caspase-12 expression levels in H9c2 cells induced by 3 h of hypoxia and 3 h of reoxygenation.

Serum uric acid and risk of incident hypercholesterolaemia and hypertriglyceridaemia in middle-aged and older Chinese: a 4-year prospective cohort study

PURPOSE

The aim was to investigate whether serum uric acid (SUA) was associated with incident hypercholesterolaemia and hypertriglyceridaemia in middle-aged and older Chinese.

METHODS

This prospective cohort study used data from the China Health and Retirement Longitudinal Study. A total of 6,063 participants were included, who were free of hypercholesterolaemia and hypertriglyceridaemia at baseline (2011) and were followed until 2015. Natural cubic spline models were conducted to investigate the dose-response association of SUA with incident hypercholesterolaemia and hypertriglyceridaemia. Moreover, SUA was categorized into four groups according to gender-specific quartiles. Log-binomial regression was performed to explore the association of SUA with hypercholesterolaemia and hypertriglyceridaemia, with the quartile 1 as a reference.

RESULTS

After full adjustment, we observed a positive linear dose-response relationship between SUA and hypercholesterolaemia and hypertriglyceridaemia. Compared with the quartile 1 of SUA, the adjusted risk ratios (95% confidence interval) of hypertriglyceridaemia were 1.15 (0.95-1.39), 1.23 (1.02-1.49) and 1.31 (1.08-1.59) for quartile 2-4 (p-value for trend = .004), respectively. Whereas, we failed to find SUA significantly associated with hypercholesterolaemia. Sex-stratified analyses indicated that the association of SUA with hypertriglyceridaemia was more evident in the female.

CONCLUSIONS

These findings suggest that SUA may be positively associated with incident hypertriglyceridaemia. KEY MESSAGES The natural cubic spline model showed a positive linear dose-response relationship between serum uric acid levels and hypertriglyceridaemia. Compared with the quartile 1 of SUA, the adjusted risk ratios (95% confidence interval) of hypertriglyceridaemia were 1.15 (0.95-1.39), 1.23 (1.02-1.49) and 1.31 (1.08-1.59) for quartile 2-4 (p-value for trend = .004), respectively. Sex-stratified analyses indicated that the association of serum uric acid with hypertriglyceridaemia was more evident in the female.

Dexmedetomidine Attenuates Cellular Injury and Apoptosis in H9c2 Cardiomyocytes by Regulating p-38MAPK and Endoplasmic Reticulum Stress

Background

Myocardial ischaemia-reperfusion injury (IRI) has been confirmed to induce endoplasmic reticulum stress (ERS) when myocardial cell function continues to deteriorate to a certain degree. The clinical applications of effective tested strategies are sometimes inconsistent with the applications evaluated in experiments, although reasonable mechanisms and diverse signalling pathways have been broadly explored. Dexmedetomidine (DEX) has been shown to attenuate IRI of the heart in animal studies. This study aimed to determine whether DEX can protect injured cardiomyocytes under hypoxia/reoxygenation (H/R) at the cellular level and whether the mechanism is related to ERS and the p38 MAPK pathway.

Methods

H9c2 cells were subjected to H/R or thapsigargin (TG) to build a model. DEX or 4-PBA was added to the medium either 1 h or 24 h before modelling, respectively. Model parameters were determined by assessing cell viability and injury, which were measured by assessing cell counting kit-8 (CCK8), lactate dehydrogenase (LDH) release and flow cytometry results, and the expression of GRP78, CHOP and caspase-12. In addition, the protein expression of p38MAPK and p-p38MAPK was examined, and SB202190, a negative regulator, was also preincubated in medium.

Results

Compared to that of cells in the control group, the activity of cells in the H/R and TG groups was decreased dramatically, and the LDH concentration and proportion of apoptotic cells were increased. DEX could correspondingly reverse the changes induced by H/R or TG. Additionally, DEX effectively attenuated ERS defined as increased expression of GRP78, CHOP and caspase-12. Additionally, DEX could obviously depress the P38 MAPK phosphorylation and high p-p38 MAPK expression in the TG group, indicating DEX has a function similar to that of SB202190.

Conclusion

H/R injury in H9c2 cells can lead to abnormal ERS and apoptosis, as well as activation of the p38MAPK signalling pathway. DEX can protect cardiomyocytes by intervening in ERS, regulating p38MAPK and the downstream apoptotic signalling pathway.

The Effects of Dexmedetomidine Post-Conditioning on Cardiac and Neurological Outcomes After Cardiac Arrest and Resuscitation in Swine

INTRODUCTION

One of the main contents of post-resuscitation care is to alleviate cardiac and neurological damage in cardiac arrest (CA) victims. Recently, dexmedetomidine pre- and post-conditioning have been shown to both effectively protect the heart and brain against regional ischemia reperfusion injury. In this study, we investigated the effects of dexmedetomidine post-conditioning on cardiac and neurological outcomes after CA and resuscitation in swine.

METHODS

A total of 28 male domestic swine were randomized into four groups: sham, cardiopulmonary resuscitation (CPR), low-dose dexmedetomidine post-conditioning (LDP), and high-dose dexmedetomidine post-conditioning (HDP). Sham animals underwent the surgical preparation only. The animal model was established by 8 min of CA and then 5 min of CPR. After the animal was successfully resuscitated, a loading dose of 0.25 μg/kg of dexmedetomidine was intravenously injected followed by continuous infusion of 0.25 μg/kg/h for 6 h in the LDP group, and meanwhile a double dose of dexmedetomidine was similarly administered in the HDP group. The same amount of saline was given in the other two groups. All the resuscitated animals were monitored for 6 h and then returned to their cages for an additional 18 h of observation.

RESULTS

After resuscitation, significantly greater cardiac, neurological dysfunction, and injuries were observed in all animals experiencing CA and resuscitation when compared with the sham group. However, the severity of cardiac and neurological damage was significantly milder in the two dexmedetomidine-treated groups than in the CPR group. Dexmedetomidine post-conditioning also significantly decreased post-resuscitation tissue inflammation, oxidative stress, and cell apoptosis and necroptosis in the heart and brain when compared with the CPR group. In addition, these protective effects produced by dexmedetomidine post-conditioning were significantly greater in the HDP group than in the LDP group.

CONCLUSIONS

Dexmedetomidine post-conditioning dose-dependently improved post-resuscitation cardiac and neurological outcomes through the inhibition of tissue inflammation, oxidative stress, and cell apoptosis and necroptosis.

[The potential role of calnexin in the activation of cardiac fibroblasts]

Calnexin is a lectin-like molecular chaperone protein on the endoplasmic reticulum, mediating unfolded protein responses, the endoplasmic reticulum Ca 2+ homeostasis, and Ca 2+ signals conduction. In recent years, studies have found that calnexin plays a key role in the heart diseases. This study aims to explore the role of calnexin in the activation of cardiac fibroblasts. A transverse aortic constriction (TAC) mouse model was established to observe the activation of cardiac fibroblasts in vivo, and the in vitro cardiac fibroblasts activation model was established by transforming growth factor β1 (TGFβ1) stimulation. The adenovirus was respectively used to gene overexpression and silencing calnexin in cardiac fibroblasts to elucidate the relationship between calnexin and cardiac fibroblasts activation, as well as the possible underlying mechanism. We confirmed the establishment of TAC model by echocardiography, hematoxylin-eosin, Masson, and Sirius red staining, and detecting the expression of cardiac fibrosis markers in cardiac tissues. After TGFβ1 stimulation, markers of the activation of cardiac fibroblast, and proliferation and migration of cardiac fibroblast were detected by quantitative PCR, Western blot, EdU assay, and wound healing assay respectively. The results showed that the calnexin expression was reduced in both the TAC mice model and the activated cardiac fibroblasts. The overexpression of calnexin relieved cardiac fibroblasts activation, in contrast, the silencing of calnexin promoted cardiac fibroblasts activation. Furthermore, we found that the endoplasmic reticulum stress was activated during cardiac fibroblasts activation, and endoplasmic reticulum stress was relieved after overexpression of calnexin. Conversely, after the silencing of calnexin, endoplasmic reticulum stress was further aggravated, accompanying with the activation of cardiac fibroblasts. Our data suggest that the overexpression of calnexin may prevent cardiac fibroblasts against activation by alleviating endoplasmic reticulum stress.

Extracellular Vesicles Derived from Human Umbilical Cord Mesenchymal Stromal Cells Protect Cardiac Cells Against Hypoxia/Reoxygenation Injury by Inhibiting Endoplasmic Reticulum Stress via Activation of the PI3K/Akt Pathway

Endoplasmic reticulum (ER) stress is implicated in the pathogenesis of many diseases, including myocardial ischemia/reperfusion injury. We hypothesized that human umbilical cord mesenchymal stromal cells derived extracellular vesicles (HuMSC-EVs) could protect cardiac cells against hyperactive ER stress induced by hypoxia/reoxygenation (H/R) injury. The H/R model was generated using the H9c2 cultured cardiac cell line. HuMSC-EVs were extracted using a commercially available exosome isolation reagent. Levels of apoptosis-related signaling molecules and the degree of ER stress were assessed by western blot. The role of the PI3K/Akt pathway was investigated using signaling inhibitors. Lactate dehydrogenase leakage and 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) analysis were used for evaluating the therapeutic effects of HuMSC-EVs in vitro. The results showed that ER stress and the rate of apoptosis were increased in the context of H/R injury. Treatment with HuMSC-EVs inhibited ER stress and increased survival in H9c2 cells exposed to H/R. Mechanistically, the PI3K/Akt pathway was activated by treatment with HuMSC-EVs after H/R. Inhibition of the PI3K/Akt pathway by a specific inhibitor, LY294002, partially reduced the protective effect of HuMSC-EVs. Our findings suggest that HuMSC-EVs could alleviate ER stress-induced apoptosis during H/R via activation of the PI3K/Akt pathway.