Hypoxic preconditioning protects microvascular endothelial cells against hypoxia/reoxygenation injury by attenuating endoplasmic reticulum stress

Acid sphingomyelinase inhibition induces cerebral angiogenesis post-ischemia/reperfusion in an oxidative stress-dependent way and promotes endothelial survival by regulating mitochondrial metabolism

Acid sphingomyelinase (ASM) inhibitors are widely used for the treatment of post-stroke depression. They promote neurological recovery in animal stroke models via neurorestorative effects. In a previous study, we found that antidepressants including amitriptyline, fluoxetine, and desipramine increase cerebral angiogenesis post-ischemia/reperfusion (I/R) in an ASM-dependent way. To elucidate the underlying mechanisms, we investigated the effects of the functional ASM inhibitor amitriptyline in two models of I/R injury, that is, in human cerebral microvascular endothelial hCMEC/D3 cells exposed to oxygen-glucose deprivation and in mice exposed to middle cerebral artery occlusion (MCAO). In addition to our earlier studies, we now show that amitriptyline increased mitochondrial reactive oxygen species (ROS) formation in hCMEC/D3 cells and increased ROS formation in the vascular compartment of MCAO mice. ROS formation was instrumental for amitriptyline's angiogenic effects. ROS formation did not result in excessive endothelial injury. Instead, amitriptyline induced a profound metabolic reprogramming of endothelial cells that comprised reduced endothelial proliferation, reduced mitochondrial energy metabolism, reduced endoplasmic reticulum stress, increased autophagy/mitophagy, stimulation of antioxidant responses and inhibition of apoptotic cell death. Specifically, the antioxidant heme oxygenase-1, which was upregulated by amitriptyline, mediated amitriptyline's angiogenic effects. Thus, heme oxygenase-1 knockdown severely compromised angiogenesis and abolished amitriptyline's angiogenic responses. Our data demonstrate that ASM inhibition reregulates a complex network of metabolic and mitochondrial responses post-I/R that contribute to cerebral angiogenesis without compromising endothelial survival.

The Unfolded Protein Response: A Double-Edged Sword for Brain Health

Efficient brain function requires as much as 20% of the total oxygen intake to support normal neuronal cell function. This level of oxygen usage, however, leads to the generation of free radicals, and thus can lead to oxidative stress and potentially to age-related cognitive decay and even neurodegenerative diseases. The regulation of this system requires a complex monitoring network to maintain proper oxygen homeostasis. Furthermore, the high content of mitochondria in the brain has elevated glucose demands, and thus requires a normal redox balance. Maintaining this is mediated by adaptive stress response pathways that permit cells to survive oxidative stress and to minimize cellular damage. These stress pathways rely on the proper function of the endoplasmic reticulum (ER) and the activation of the unfolded protein response (UPR), a cellular pathway responsible for normal ER function and cell survival. Interestingly, the UPR has two opposing signaling pathways, one that promotes cell survival and one that induces apoptosis. In this narrative review, we discuss the opposing roles of the UPR signaling pathways and how a better understanding of these stress pathways could potentially allow for the development of effective strategies to prevent age-related cognitive decay as well as treat neurodegenerative diseases.

Intermittent Hypoxic Preconditioning Plays a Cardioprotective Role in Doxorubicin-Induced Cardiomyopathy

Intermittent hypoxic preconditioning (IHP) is a well-established cardioprotective intervention in models of ischemia/reperfusion injury. Nevertheless, the significance of IHP in different cardiac pathologies remains elusive. In order to investigate the role of IHP and its effects on calcium-dependent signalization in HF, we employed a model of cardiomyopathy induced by doxorubicin (Dox), a widely used drug from the class of cardiotoxic antineoplastics, which was i.p. injected to Wistar rats (4 applications of 4 mg/kg/week). IHP-treated group was exposed to IHP for 2 weeks prior to Dox administration. IHP ameliorated Dox-induced reduction in cardiac output. Western blot analysis revealed increased expression of sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA2a) while the expression of hypoxia inducible factor (HIF)-1-α, which is a crucial regulator of hypoxia-inducible genes, was not changed. Animals administered with Dox had further decreased expression of TRPV1 and TRPV4 (transient receptor potential, vanilloid subtype) ion channels along with suppressed Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) activation. In summary, IHP-mediated improvement in cardiac output in the model of Dox-induced cardiomyopathy is likely a result of increased SERCA2a expression which could implicate IHP as a potential protective intervention in Dox cardiomyopathy, however, further analysis of observed effects is still required.

Gardenia jasminoides Extract GJ-4 Alleviates Memory Deficiency of Vascular Dementia in Rats through PERK-Mediated Endoplasmic Reticulum Stress Pathway

Endoplasmic reticulum stress (ERS) is involved in the pathological process of vascular dementia (VD). GJ-4 is extracted from Gardenia jasminoides J. Ellis and has been reported to have protective roles in ischemia-related brain damage. However, the role of GJ-4 in ERS has not been elucidated. We established a VD rat model through bilateral common carotid arteries occlusion (2-VO). The rats were intragastrically administrated with GJ-4 (10, 25, and 50[Formula: see text]mg/kg) and nimodipine (10[Formula: see text]mg/kg). Data from a Morris water maze test showed that GJ-4 could significantly alleviate learning and memory deficits in VD rats. Nissl and cleaved caspase-3 staining revealed that GJ-4 can inhibit apoptosis and thus exert a protective role in the brain of 2-VO rats. Western blot results suggested that GJ-4 significantly reduced ERS-related protein expression and inhibited apoptosis through suppression of the PERK/eIF2[Formula: see text]/ATF4/CHOP signaling pathway. For in vitro studies, the oxygen-glucose deprivation (OGD) SH-SY5Y model was employed. Western blot and Hoechst 33342/PI double staining were utilized to explore the effects of crocetin, the main active metabolite of GJ-4. Like GJ-4 in vivo, crocetin in vitro also decreased ERS-related protein expression and inhibited the activation of the PERK/eIF2[Formula: see text]/ATF4/CHOP signaling pathway. Thus, crocetin exerted similar protective roles on OGD challenged SH-SY5Y cells in vitro. In summary, GJ-4 and crocetin reduce the ERS in the brain of VD rats and SY5Y cells subjected to OGD and inhibit neuronal apoptosis through suppression of the PERK/eIF2[Formula: see text]/ATF4/CHOP pathway, suggesting that GJ-4 may be useful for the treatment of VD.

The Role of the Hypoxia-Related Unfolded Protein Response (UPR) in the Tumor Microenvironment

Despite our understanding of the unfolded protein response (UPR) pathways, the crosstalk between the UPR and the complex signaling networks that different cancers utilize for cell survival remains to be, in most cases, a difficult research barrier. A major problem is the constant variability of different cancer types and the different stages of cancer as well as the complexity of the tumor microenvironments (TME). This complexity often leads to apparently contradictory results. Furthermore, the majority of the studies that have been conducted have utilized two-dimensional in vitro cultures of cancer cells that were exposed to continuous hypoxia, and this approach may not mimic the dynamic and cyclic conditions that are found in solid tumors. Here, we discuss the role of intermittent hypoxia, one of inducers of the UPR in the cellular component of TME, and the way in which intermittent hypoxia induces high levels of reactive oxygen species, the activation of the UPR, and the way in which cancer cells modulate the UPR to aid in their survival. Although the past decade has resulted in defining the complex, novel non-coding RNA-based regulatory networks that modulate the means by which hypoxia influences the UPR, we are now just to beginning to understand some of the connections between hypoxia, the UPR, and the TME.

Irisin protects cardiomyocytes against hypoxia/reoxygenation injury via attenuating AMPK mediated endoplasmic reticulum stress

Endoplasmic reticulum (ER) stress plays a central role in myocardial ischemia/reperfusion (I/R) injury. Irisin has been reported to have protective properties in ischemia disease. In this study, we aimed at investigating whether irisin could alleviate myocardial I/R injury by ER stress attenuation. The in vitro model of hypoxia/reoxygenation (H/R) was established, which resembles I/R in vivo. Cell viability and apoptosis were estimated. Expressions of cleaved caspase-3, cytochrome c, GRP78, pAMPK, CHOP, and eIF2α were assessed by western blot. Our results revealed that pre-treatment with irisin significantly decreased cytochrome c release from mitochondria and caspase-3 activation caused by H/R. Irsin also reduced apoptosis and increased cell viability. These effects were abolished by AMPK inhibitor compound C pre-treatment. Also, GRP78 and CHOP expressions were up-regulated in the H/R group compared to the control group; however, irisin attenuated their expression. The pAMPK level was significantly decreased compared to the control, and this effect could be partly reversed by metformin pre-treatment. These results suggest that ER stress is associated with cell viability decreasing and cardiomyocytes apoptosis induced by H/R. Irisin could efficiently protect cardiomyocytes from H/R-injury via attenuating ER stress and ER stress-induced apoptosis.

Curcumin and cardiovascular diseases: Focus on cellular targets and cascades

Cardiovascular diseases (CVDs) are one of the leading causes of the most considerable mortality globally, and it has been tried to find the molecular mechanisms and design new drugs that triggered the molecular target. Curcumin is the main ingredient of Curcuma longa (turmeric) that has been used in traditional medicine for treating several diseases for years. Numerous investigations have indicated the beneficial effect of Curcumin in modulating multiple signaling pathways involved in oxidative stress, inflammation, apoptosis, and proliferation. The cardiovascular protective effects of Curcumin against CVDs have been indicated in several studies. In the current review study, we provided novel information on Curcumin's protective effects against various CVDs and potential molecular signaling targets of Curcumin. Nonetheless, more studies should be performed to discover the exact molecular target of Curcumin against CVDs.

Effect of endoplasmic reticulum stress on endothelial ischemia-reperfusion injury in humans

Endoplasmic reticulum stress contributes to ischemia-reperfusion (I/R) injury in rodent and cell models. However, the contribution of endoplasmic reticulum stress in the pathogenesis of endothelial I/R injury in humans is unknown. We tested the hypothesis that compared with placebo, inhibition of endoplasmic reticulum stress via ingestion of tauroursodeoxycholic acid would prevent the attenuation of endothelium-dependent vasodilation following I/R injury. Twelve young adults (6 women) were studied following ingestion of a placebo or 1,500 mg tauroursodeoxycholic acid (TUDCA). Endothelium-dependent vasodilation was assessed via brachial artery flow-mediated dilation (duplex ultrasonography) before and after I/R injury, which was induced by 20 min of arm ischemia followed by 20 min of reperfusion. Endothelium-independent vasodilation (glyceryl trinitrate-mediated vasodilation) was also assessed after I/R injury. Compared with placebo, TUDCA ingestion increased circulating plasma concentrations by 145 ± 90 ng/ml and increased concentrations of the taurine unconjugated form, ursodeoxycholic acid, by 560 ± 156 ng/ml (both P < 0.01). Ischemia-reperfusion injury attenuated endothelium-dependent vasodilation, an effect that did not differ between placebo (pre-I/R, 5.0 ± 2.1% vs. post-I/R, 3.5 ± 2.2%) and TUDCA (pre-I/R, 5.6 ± 2.1% vs. post-I/R, 3.9 ± 2.1%; P = 0.8) conditions. Similarly, endothelium-independent vasodilation did not differ between conditions (placebo, 19.6 ± 4.8% vs. TUDCA, 19.7 ± 6.1%; P = 0.9). Taken together, endoplasmic reticulum stress does not appear to contribute to endothelial I/R injury in healthy young adults.

Unfolded protein response (UPR) integrated signaling networks determine cell fate during hypoxia

During hypoxic conditions, cells undergo critical adaptive responses that include the up-regulation of hypoxia-inducible proteins (HIFs) and the induction of the unfolded protein response (UPR). While their induced signaling pathways have many distinct targets, there are some important connections as well. Despite the extensive studies on both of these signaling pathways, the exact mechanisms involved that determine survival versus apoptosis remain largely unexplained and therefore beyond therapeutic control. Here we discuss the complex relationship between the HIF and UPR signaling pathways and the importance of understanding how these pathways differ between normal and cancer cell models.

Curcumin attenuates hypoxia/reoxygenation‑induced myocardial injury

Curcumin (Cur) has been reported to function as an antioxidant and anti-inflammatory agent and to play a role in anti-atherosclerosis. The present study aimed to explore the protective effect of Cur on hypoxia/reoxygenation (H/R) injury. The morphological changes in H9c2 cardiomyocytes were observed under an inverted microscope. Cell viability was determined by Cell Counting Kit-8 (CCK-8). Lactate dehydrogenase (LDH) level, malondialdehyde (MDA) level and the antioxidant superoxide dismutase (SOD) activity were determined by corresponding kits. Apoptosis and reactive oxygen species (ROS) levels were determined by flow cytometry. Endoplasmic reticulum (ER) stress-related factors, which were examined by quantitative real-time polymerase chain reaction (qPCR) and western blot analysis, included 78-kDa glucose-regulated protein (GRP78) and C/EBP homologous protein (CHOP). Extracellular signal regulating kinase 1/2 (ERK1/2), p38, c-Jun NH2-terminal kinase (JNK) and the phosphorylation levels of key proteins in the mitogen-activated protein kinase (MAPK) signaling pathway were all determined by western blot analysis. Compared to the control group, the cell morphology of the H9c2 cells was obviously altered upon H/R. Cell viability was significantly decreased, while apoptosis was significantly increased by H/R. We also observed that the levels of LDH and MDA were elevated and the activity of SOD was decreased in the H/R group. Notably, LDH, MDA and SOD levels were reversed following treatment with Cur; while apoptosis and ROS levels in the H/R injury group were decreased by Cur. H/R injury-triggered ER stress and the MAPK signaling pathway were suppressed by Cur. These results demonstrated that Cur has a protective effect on cardiomyocytes via suppression of ER stress and the MAPK pathway.

TIR/BB-loop mimetic AS-1 protects vascular endothelial cells from injury induced by hypoxia/reoxygenation

Morphological and functional abnormalities of vascular endothelial cells (VECs) are risk factors of ischemia-reperfusion in skin flaps. Signaling pathway mediated by interleukin-1 receptor (IL-1R) is essential to hypoxia/reoxygenation (H/R) injury of VECs. While the TIR/BB-loop mimetic (AS-1) disrupts the interaction between IL-1R and myeloid differentiation primary-response protein 88 (MyD88), its role in the VECs dysfunction under H/R is unclear. In this study, we first showed that there was an infiltration of inflammatory cells and the apoptosis of VECs by using a skin flap section from patients who received flap transplantation. We then showed that the H/R treatment induced apoptosis and loss of cell migration of endothelial cell line H926 were attenuated by AS-1. Furthermore, our data suggested that AS-1 inhibits the interaction between IL-1R and MyD88, and subsequent phosphorylation of IκB and p38 pathway, as well as the nuclear localization of NF-KB subunit p65/p50. Thus, this study indicated that the protective role of AS-1 in H/R induced cellular injury may be due to the AS-1 mediated down-regulation of IL-1R signaling pathway.

Regulatory Mechanisms of the NLRP3 Inflammasome, a Novel Immune-Inflammatory Marker in Cardiovascular Diseases

The nod-like receptor family pyrin domain containing 3 (NLRP3) is currently the most widely studied inflammasome and has become a hot topic of recent research. As a macromolecular complex, the NLRP3 inflammasome is activated to produce downstream factors, including caspase-1, IL-1β, and IL-18, which then promote local inflammatory responses and induce pyroptosis, leading to unfavorable effects. A growing number of studies have examined the relationship between the NLRP3 inflammasome and cardiovascular diseases (CVDs). However, some studies have shown that the NLRP3 inflammasome is not involved in the occurrence of certain diseases. Therefore, identifying the mechanism of action of the NLRP3 inflammasome and its potential involvement in the pathological process of disease progression is of utmost importance. This review discusses the mechanisms of NLRP3 inflammasome activation and the relationship between the inflammasome and CVDs, including coronary atherosclerosis, myocardial ischemia/reperfusion, cardiomyopathies, and arrhythmia, as well as CVD-related treatments.

RETRACTED: Matrine inhibits hypoxia/reoxygenation-induced apoptosis of cardiac microvascular endothelial cells in rats via the JAK2/STAT3 signaling pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. An Expression of Concern for this article was previously published while an investigation was conducted (see related editorial: https://doi.org/10.1016/j.biopha.2022.113812). This retraction notice supersedes the Expression of Concern published earlier. Concerns were raised about the provenance of the flow cytometry data shown in Figure 5A, as detailed here: https://pubpeer.com/publications/46C8B5439C5C617A60494BA4C15479; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Independent analysis also identified additional suspected image duplications between the Bax and Bcl-2 Western blots in Figure 6A. The journal requested the corresponding author comment on these concerns and provide the associated raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

Tauroursodeoxycholic Acid Alleviates H2O2-Induced Oxidative Stress and Apoptosis via Suppressing Endoplasmic Reticulum Stress in Neonatal Rat Cardiomyocytes

Introduction:

We aimed to test the mechanism of protective effects of tauroursodeoxycholic acid (TUDCA) on cardiovascular disease using cultured cardiomyocytes.

Methods:

Neonatal rat cardiomyocytes (NRCMs) were isolated and cultured and then the cells were divided into 4 groups based on the treatments: control group (cells treated with culture medium), H₂O₂/thapsigargin (TG) group (cells treated with oxidative stress and endoplasmic reticulum [ER] stress inducer), TUDCA group, and H₂O₂/TG + TUDCA group. The treated NRCMs were then subjected to serial analyses including flow cytometry, enzyme-linked immunosorbent assay, and Western blotting.

Results:

Tauroursodeoxycholic acid significantly attenuated H₂O₂-induced reactive oxygen species generation and lactate dehydrogenase release and restored H₂O₂-induced reductions of glutathione and superoxide dismutase levels in NRCMs. Tauroursodeoxycholic acid also alleviated H₂O₂-induced cardiomyocytes apoptosis, as well as the Bax/Bcl2 ratio compared with that of H₂O₂ treated alone. In addition, TUDCA suppressed TG-induced ER stress as reflected by inversing cell viability and the expression levels of glucose-regulated protein 78 kDa and C/enhancer-binding protein homologous protein.

Conclusion:

Our data indicated that TUDCA-mediated inhibition on H₂O₂-induced oxidative stress and cardiomyocytes apoptosis was through suppressing ER stress, and TUDCA possesses the potential to be developed as therapeutic tool in clinical use for cardiovascular diseases.

Endoplasmic reticulum (ER) stress triggers Hax1-dependent mitochondrial apoptotic events in cardiac cells

Cardiomyocyte apoptosis is a major process in pathogenesis of a number of heart diseases, including ischemic heart diseases and cardiac failure. Ensuring survival of cardiac cells by blocking apoptotic events is an important strategy to improve cardiac function. Although the role of ER disruption in inducing apoptosis has been demonstrated, we do not yet fully understand how it influences the mitochondrial apoptotic machinery in cardiac cell models. Recent investigations have provided evidences that the prosurvival protein HCLS1-associated protein X-1 (Hax1) protein is intimately associated with the pathogenesis of heart disease, mitochondrial biology, and protection from apoptotic cell death. To study the role of Hax1 upon ER stress induction, Hax1 was overexpressed in cardiac cells subjected to ER stress, and cell death parameters as well as mitochondrial alterations were examined. Our results demonstrated that the Hax1 is significantly downregulated in cardiac cells upon ER stress induction. Moreover, overexpression of Hax1 protected from apoptotic events triggered by Tunicamycin-induced ER stress. Upon treatment with Tunicamycin, Hax1 protected from mitochondrial fission, downregulation of mitofusins 1 and 2 (MFN1 and MFN2), loss of mitochondrial membrane potential (∆Ψm), production of reactive oxygen species (ROS) and apoptotic cell death. Taken together, our results suggest that Hax1 inhibits ER stress-induced apoptosis at both the pre- and post-mitochondrial levels. These findings may offer an opportunity to develop new agents that inhibit cell death in the diseased heart.

Hydrogen Sulfide Inhibits Cigarette Smoke-Induced Endoplasmic Reticulum Stress and Apoptosis in Bronchial Epithelial Cells

Background: Apoptosis of lung structural cells contributes to the process of lung damage and remodeling in chronic obstructive pulmonary disease (COPD). Our previous studies demonstrated that exogenous hydrogen sulfide (H₂S) can reduce the lung tissue pathology score, anti-inflammation and anti-oxidation effects in COPD, but the effect of H₂S in regulating cigarette smoke (CS) induced bronchial epithelial cell apoptosis and the underlying mechanisms are not clear.

Objectives: To investigate the effect of H₂S on CS induced endoplasmic reticulum stress (ERS) and bronchial epithelial cell apoptosis.

Methods: Male Sprague–Dawley rats randomly divided into four groups for treatment: control, CS, NaHS + CS, and propargylglycine (PPG) + CS. The rats in the CS group were exposed to CS generated from 20 commercial unfiltered cigarettes for 4 h/day, 7 days/week for 4 months. Since the beginning of the third month, freshly prepared NaHS (14 μmol/kg) and PPG (37.5 mg/kg) were intraperitoneally administered 30 min before CS-exposure in the NaHS and PPG groups. 16HBE cells were pretreated with Taurine (10 mM), 5 mmol/L 4-phenylbutyric acid (4-PBA) or NaHS (100, 200, and 400 μM) for 30 min, and then cells were exposed to 40 μmol/L nicotine for 72 h. ERS markers (GRP94, GRP78) and ERS-mediated apoptosis markers 4-C/EBP homologous protein (CHOP), caspase-3 and caspase-12 were assessed in rat lung tissues and human bronchial epithelial cells. The apoptotic bronchial epithelial cells were detected by Hoechst staining in vitro and TUNEL staining in vivo.

Results: In CS exposed rats, peritoneal injection of NaHS significantly inhibited CS induced overexpression ERS-mediated apoptosis markers and upregulation of apoptotic rate in rat lungs, and inhibiting the endogenous H2S production by peritoneal injection of PPG exacerbated these effects. In the nicotine-exposed bronchial epithelial cells, appropriate concentration of NaHS and ERS inhibitors taurine and 4-PBA inhibited nicotine-induced upregulation of apoptotic rate and overexpression of ERS-mediated apoptosis markers.

Conclusion: H₂S inhibited lung tissue damage by attenuating CS induced ERS in rat lung and exogenous H₂S attenuated nicotine induced ERS-mediated apoptosis in bronchial epithelial cells.

Bisoprolol protects myocardium cells against ischemia/reperfusion injury by attenuating unfolded protein response in rats

Bisoprolol (B) exerts potential cardioprotective effects against myocardial ischemia/reperfusion (I/R) injury. Unfolded protein response (UPR) attenuates I/R injury induced apoptosis by reducing oxidative damage and inflammation response. The current study investigated whether the protective effects of bisoprolol resulted from modulating UPR and anti-inflammatory during myocardial I/R condition and elucidated its potential mechanisms. Sprague-Dawley rats were treated with B in the absence or presence of the injected UPR activator dithiothreitol (DTT) and then subjected to myocardial I/R surgery. In vitro, cultured H9C2 cells were pretreated with B or DTT and then subjected to simulate ischemia reperfusion (SIR) operation. Bisoprolol conferred cardioprotective effects by improving postischemic cardiac function, decreasing infarct size, reducing apoptotic index, diminishing serum creatine kinase and lactate dehydrogenase levels, suppressing TNF-α and IL-6 secretion, inhibiting UPR signal pathways and downregulating caspase-12 and caspase-3 expressions. Consistently, B conferred similar antioxidative and anti-inflammatory effects against SIR injury in cultured H9C2 cardiomyocytes. Pretreatment with DTT or C/EBP homologous protein (CHOP) overexpression mediated by lentivirus administration both abolished these effects. In summary, our results demonstrate that Bisoprolol protects myocardium cells against ischemia/reperfusion injury partly by attenuating unfolded protein response.

Liraglutide protects cardiac microvascular endothelial cells against hypoxia/reoxygenation injury through the suppression of the SR-Ca(2+)-XO-ROS axis via activation of the GLP-1R/PI3K/Akt/survivin pathways

Microvascular endothelial cells (CMECs) oxidative damage resulting from hypoxia/reoxygenation (H/R) injury is responsible for microcirculation perfusion disturbances and the progression of cardiac dysfunction. However, few strategies are available to reverse such pathologies. Here, we studied the effects and mechanisms of liraglutide on CEMCs oxidative damage, focusing in particular on calcium overload-triggered free radical injury signals and the GLP-1R/PI3K/Akt/survivin survival pathways. The results indicate that H/R increased IP3R expression but reduced SERCA2a expression, which rapidly raised intracellular Ca(2+) levels, subsequently leading to Ca(2+)-dependent xanthine oxidase (XO) activation, reactive oxygen species (ROS) production and the cellular apoptosis of CMECs. However, liraglutide pretreatment abrogated Ca(2+)-mediated oxidative apoptosis. Furthermore, liraglutide regulated the rate of IP3R/SERCA2a gene transcription and conserved SERCA2a-ATPase activity via the maintenance of ATP production under H/R, which drove excessive Ca(2+) reflux to the sarcoplasmic reticulum (SR) and inhibited Ca(2+) release from the SR, ultimately restoring Ca(2+) homeostasis. Furthermore, the regulatory role of liraglutide on Ca(2+) balance in conjunction with its up-regulation of superoxide dismutase, glutathione and glutathione peroxidase collectively scavenged the excess ROS under H/R. Moreover, we showed that liraglutide strengthened Akt phosphorylation and subsequently survivin expression. In addition, both the blockade of the GLP-1R/PI3K/Akt pathways and the siRNA-mediated knockdown of survivin abolished the protective effects of liraglutide on SR-Ca(2+) function and CMECs oxidative apoptosis. In summary, this study confirmed that H/R induced CMECs oxidative damage through the SR-Ca(2+)-XO-ROS injury signals and that liraglutide pretreatment may suppress such CMECs damage through the PI3K/Akt/survivin pathways.

Berberine protects rat heart from ischemia/reperfusion injury via activating JAK2/STAT3 signaling and attenuating endoplasmic reticulum stress

AIM

Berberine (BBR), an isoquinoline-derived alkaloid isolated from Rhizoma coptidis, exerts cardioprotective effects. Because endoplasmic reticulum (ER) stress plays a pivotal role in myocardial ischemia/reperfusion (MI/R)-induced apoptosis, it was interesting to examine whether the protective effects of BBR resulted from modulating ER stress levels during MI/R injury, and to define the signaling mechanisms in this process.

METHODS

Male rats were treated with BBR (200 mg · kg(-1) · d(-1), ig) for 2 weeks, and then subjected to MI/R surgery. Cardiac dimensions and function were assessed using echocardiography. Myocardial infarct size and apoptosis was examined. Total serum LDH levels and CK activities, superoxide production, MDA levels and the antioxidant SOD activities in heart tissue were determined. An in vitro study was performed on cultured rat embryonic myocardium-derived cells H9C2 exposed to simulated ischemia/reperfusion (SIR). The expression of apoptotic, ER stress-related and signaling proteins were assessed using Western blot analyses.

RESULTS

Pretreatment with BBR significantly reduced MI/R-induced myocardial infarct size, improved cardiac function, and suppressed myocardial apoptosis and oxidative damage. Furthermore, pretreatment with BBR suppressed MI/R-induced ER stress, evidenced by down-regulating the phosphorylation levels of myocardial PERK and eIF2α and the expression of ATF4 and CHOP in heart tissues. Pretreatment with BBR also activated the JAK2/STAT3 signaling pathway in heart tissues, and co-treatment with AG490, a specific JAK2/STAT3 inhibitor, blocked not only the protective effects of BBR, but also the inhibition of BBR on MI/R-induced ER stress. In H9C2 cells, treatment with BBR (50 μmol/L) markedly reduced SIR-induced cell apoptosis, oxidative stress and ER stress, which were abolished by transfection with JAK2 siRNA.

CONCLUSION

BBR ameliorates MI/R injury in rats by activating the AK2/STAT3 signaling pathway and attenuating ER stress-induced apoptosis.

Myofibrillogenesis regulator-1 attenuated hypoxia/reoxygenation-induced apoptosis by inhibiting the PERK/Nrf2 pathway in neonatal rat cardiomyocytes

The purpose of this study was to investigate the role of myofibrillogenesis regulator-1 (MR-1) in cardiomyocyte apoptosis induced by hypoxia/reoxygenation (H/R), through protein kinase R-like ER kinase (PERK)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. To address this aim, an H/R model of neonatal rat cardiomyocytes was used. MR-1 was overexpressed using an adenoviral vector system and knocked down using MR-1 specific siRNA. Apoptosis was assessed by using Annexin V/PI double staining, terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling assay, and the Bcl-2/Bax ratio. Western blotting was used to detect the protein levels of MR-1, glucose-regulated protein 78 (GRP78), total and phosphorylated PERK, Nrf2, activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), Bcl-2 and Bax. Immunofluorescence staining was used to assess the subcellular location of Nrf2. We found that H/R induced significant apoptosis in neonatal rat cardiomyocytes. MR-1 overexpression attenuated H/R-induced apoptosis, decreased GRP78 (P < 0.01) and CHOP expression (P < 0.05), and increased the Bcl-2/Bax ratio (P < 0.01). MR-1 overexpression suppressed H/R-induced PERK phosphorylation, Nrf2 nuclear translocation, and ATF4 expression (P < 0.01). While MR-1 knockdown aggravated H/R-induced apoptosis, increased expression of GRP78 and CHOP (P < 0.05), and decreased the Bcl-2/Bax ratio (P < 0.01). MR-1 knockdown significantly increased H/R-induced PERK phosphorylation (P < 0.05), Nrf2 nuclear translocation, and ATF4 expression (P < 0.01). These findings suggest that MR-1 alleviates H/R-induced cardiomyocyte apoptosis through inhibition of the PERK/Nrf2 pathway.

Elatoside C protects against hypoxia/reoxygenation-induced apoptosis in H9c2 cardiomyocytes through the reduction of endoplasmic reticulum stress partially depending on STAT3 activation

Endoplasmic reticulum (ER) stress-induced apoptosis has been suggested to contribute to myocardial ischemia-reperfusion (I/R) injury. Elatoside C is one of the major triterpenoid compounds isolated from Aralia elata that is known to be cardioprotective. However, its effects on I/R injury to cardiac myocytes have not been clarified. This study aimed to investigate the possible protective effect of Elatoside C against hypoxia/reoxygenation (H/R)-induced H9c2 cardiomyocyte injury and its underlying mechanisms. H9c2 cardiomyocytes were subjected to H/R in the presence of Elatoside C. Our results showed that Elatoside C (25 μM) treatment provided significant protection against H/R-induced cell death, as evidenced by improved cell viability, maintained mitochondrial membrane potential, diminished mitochondrial ROS, and reduced apoptotic cardiomyocytes (P < 0.05). These changes were associated with the inhibition of ER stress-associated apoptosis markers (GRP78, CHOP, Caspase-12 and JNK), as well as the increased phosphorylation of STAT3 and an increased Bcl2/Bax ratio. Moreover, these effects of Elatoside C were prevented by the STAT3 inhibitor Stattic. Taken together, these results suggested that Elatoside C can alleviate H/R-induced cardiomyocyte apoptosis most likely by activating the STAT3 pathways and reducing ER stress-associated apoptosis.

Lycopene Protects against Hypoxia/Reoxygenation Injury by Alleviating ER Stress Induced Apoptosis in Neonatal Mouse Cardiomyocytes

Endoplasmic reticulum (ER) stress induced apoptosis plays a pivotal role in myocardial ischemia/reperfusion (I/R)-injury. Inhibiting ER stress is a major therapeutic target/strategy in treating cardiovascular diseases. Our previous studies revealed that lycopene exhibits great pharmacological potential in protecting against the I/R-injury in vitro and vivo, but whether attenuation of ER stress (and) or ER stress-induced apoptosis contributes to the effects remains unclear. In the present study, using neonatal mouse cardiomyocytes to establish an in vitro model of hypoxia/reoxygenation (H/R) to mimic myocardium I/R in vivo, we aimed to explore the hypothesis that lycopene could alleviate the ER stress and ER stress-induced apoptosis in H/R-injury. We observed that lycopene alleviated the H/R injury as revealed by improving cell viability and reducing apoptosis, suppressed reactive oxygen species (ROS) generation and improved the phosphorylated AMPK expression, attenuated ER stress as evidenced by decreasing the expression of GRP78, ATF6 mRNA, sXbp-1 mRNA, eIF2α mRNA and eIF2α phosphorylation, alleviated ER stress-induced apoptosis as manifested by reducing CHOP/GADD153 expression, the ratio of Bax/Bcl-2, caspase-12 and caspase-3 activity in H/R-treated cardiomyocytes. Thapsigargin (TG) is a potent ER stress inducer and used to elicit ER stress of cardiomyocytes. Our results showed that lycopene was able to prevent TG-induced ER stress as reflected by attenuating the protein expression of GRP78 and CHOP/GADD153 compared to TG group, significantly improve TG-caused a loss of cell viability and decrease apoptosis in TG-treated cardiomyocytes. These results suggest that the protective effects of lycopene on H/R-injury are, at least in part, through alleviating ER stress and ER stress-induced apoptosis in neonatal mouse cardiomyocytes.

Cytosolic calreticulin inhibits microwave radiation-induced microvascular endothelial cell injury through the integrin-focal adhesion kinase pathway

OBJECTIVE

To determine the effects of cytosolic CRT on MR-induced MMEC injury, and the underlying mechanism.

METHODS

MMECs were randomized into eight groups: control, AdCRT (infected with pAdCMV/V5-DEST-CRT adenovirus), stCRT (transfected with rCRT-siRNAs), Mock (transfected with scrambled siRNAs), MR (exposed to MR for six minutes), AdCRT + MR, stCRT + MR, and Mock + MR. The magnitude of cell injury were assessed by Annexin V-PI staining, LDH activity in culture medium, MMEC migration ability, ultrastructure and cytoskeletal stability. Subcellular colocalization of CRT and ConA or integrin were evaluated by immunocytochemistry. The mRNA and protein expression levels of target genes were examined by qRT-PCR and western blotting, respectively.

RESULTS

MR-induced cytotoxicity was dose-dependent. Overexpression of cytosolic CRT suppressed MR injury, shown as decreased cell apoptosis, reduced LDH activity, enhanced cell migration capability, and maintenance of ultrastructure and cytoskeleton integrity. Conversely, CRT deficiency aggravated MR-induced injury. Exposure of AdCRT MMECs to MR promoted membrane translocation of CRT and the interaction of CRT-integrin-α. Correlation analysis revealed that integrin-α expression or FAK phosphorylation was positively associated with cytosolic CRT expression.

CONCLUSIONS

Cytosolic CRT inhibits MR-induced MMEC injury through activation of the integrin-FAK pathway.

Differential Tissue-Specific Function of Adora2b in Cardioprotection

The adenosine A2b receptor (Adora2b) has been implicated in cardioprotection from myocardial ischemia. As such, Adora2b was found to be critical in ischemic preconditioning (IP) or ischemia/reperfusion (IR) injury of the heart. Whereas Adora2b is present on various cells types, the tissue-specific role of Adora2b in cardioprotection is still unknown. To study the tissue-specific role of Adora2b signaling on inflammatory cells, endothelia, or myocytes during myocardial ischemia in vivo, we intercrossed floxed Adora2b mice with Lyz2-Cre(+), VE-cadherin-Cre(+), or myosin-Cre(+) transgenic mice, respectively. Mice were exposed to 60 min of myocardial ischemia with or without IP (four times for 5 min) followed by 120 min of reperfusion. Cardioprotection by IP was abolished in Adora2b(f/f)-VE-cadherin-Cre(+) or Adora2b(f/f)-myosin-Cre(+), indicating that Adora2b signaling on endothelia or myocytes mediates IP. In contrast, primarily Adora2b signaling on inflammatory cells was necessary to provide cardioprotection in IR injury, indicated by significantly larger infarcts and higher troponin levels in Adora2b(f/f)-Lyz2-Cre(+) mice only. Cytokine profiling of IR injury in Adora2b(f/f)-Lyz2-Cre(+) mice pointed toward polymorphonuclear neutrophils (PMNs). Analysis of PMNs from Adora2b(f/f)-Lyz2-Cre(+) confirmed PMNs as one source of identified tissue cytokines. Finally, adoptive transfer of Adora2b(-/-) PMNs revealed a critical role of Adora2b on PMNs in cardioprotection from IR injury. Adora2b signaling mediates different types of cardioprotection in a tissue-specific manner. These findings have implications for the use of Adora2b agonists in the treatment or prevention of myocardial injury by ischemia.

TGF-β improves myocardial function and prevents apoptosis induced by anoxia-reoxygenation, through the reduction of endoplasmic reticulum stress

BACKGROUND

Transforming growth factor-β (TGF-β) is known for its role in ventricular remodeling, inflammatory response, cell survival, and apoptosis. However, its role in improving myocardial function in rat hearts subjected to ischemia-reperfusion (I/R) and protecting against apoptosis induced in cardiomyocytes by anoxia-reoxygenation (A/R) has not been elucidated. This study investigated the protective effects and molecular mechanisms of TGF-β on myocardial function and cardiomyocyte apoptosis.

METHODS AND RESULTS

We used TUNEL staining, we tested cell viability, and we measured mitochondrial membrane potential and levels of mitochondrial ROS after 6 h of simulated anoxia together with various durations of simulated reoxygenation in H9c2 cells. We further observed the contractile function in rat hearts after they were subjected to 30 min global ischemia and 180 min reperfusion. Pretreatment with TGF-β markedly inhibited apoptosis in H9c2 cells, as evidenced by increased cell viability and decreased numbers of TUNEL-positive cells, maintained mitochondrial membrane potential, and diminished mitochondrial production of reactive oxygen species (ROS). These changes were associated with the inhibition of endoplasmic reticulum (ER) stress-dependent markers of apoptosis (GRP78, CHOP, caspase-12, and JNK), and the modulation of the expression of Bcl2/Bax. Furthermore, TGF-β improved I/R-induced myocardial contractile dysfunction. All of these protective effects were concentration-dependent.

CONCLUSION

Our results show that TGF-β prevents A/R-induced apoptosis of cardiomyocytes and improves myocardial function in rat hearts injured by I/R.

Calreticulin protects rat microvascular endothelial cells against microwave radiation-induced injury by attenuating endoplasmic reticulum stress

OBJECTIVE

This study was designed to evaluate whether exogenous CRT was beneficial for alleviating MR-induced injury by suppressing ER stress in rat MMECs.

METHODS

MMECs were pretreated with CRT (25 pg/mL) for 12 hours, followed by the exposure to 2.856 GHz radiation at a mean power density of 30 mW/cm(2) for six minutes. MR-induced injury in MMECs was evaluated by LDH leakage, apoptosis, and cell viability analysis. The expression of GRP78, CRT, CHOP, Bcl-2, and Bax were examined by Western blot analysis to reflect ER stress response and ER stress-related apoptosis.

RESULTS

MR induced marked MMECs injury, as shown by increased LDH leakage and apoptosis rate and decreased cell viability. MR also induced excessive ER stress, characterized by increased expression of GRP78 and CRT, and ER stress-related apoptotic signaling as well, as shown by the upregulation of CHOP and Bax and the downregulation of Bcl-2. Exogenous CRT pretreatment remarkably attenuated MR-induced cell apoptosis and LDH leakage, ER stress, and activation of the ER stress-related apoptotic signaling.

CONCLUSIONS

Exogenous CRT attenuates MR-induced ER stress-related apoptosis by suppressing CHOP-mediated apoptotic signaling pathways in MMECs.

N-acyl dopamine derivates as lead compound for implementation in transplantation medicine

Conjugates of fatty acids with ethanolamine, amino acids or monoamine neurotransmitters occur widely in nature giving rise to so-called endocannabinoids. Anandamide and 2-arachidonoyl glycerol are the best characterized endocannabinoids activating both cannabinoid receptors (CB1 and CB2) and transient receptor potential vanilloid type 1 (TRPV1) channels (anandamide) or activating cannabinoid receptors only (2-arachidonoyl glycerol). TRPV1 is also activated by vanilloids, such as capsaicin, and endogenous neurolipins, e.g. N-arachidonoyl dopamine (NADA) and N-oleoyl dopamine (OLDA). Because donor dopamine treatment has shown to improve transplantation outcome in renal and heart recipients, this review will mainly focus on the biological activities of N-acyl dopamine derivates (NADD) as potential non-hemodynamic alternative for implementation in transplantation medicine. Hence the influence of NADD on transplantation relevant entities, i.e. cold inflicted injury, cytoprotection, I/R-injury, immune-modulation and inflammation will be summarized. The cytoprotective properties of endogenous endocannabinoids in this context will be briefly touched upon.

Effect of Endoplasmic Reticulum Stress on Resveratrol-Induced Cardioprotection

To investigate if resveratrol prevent the mitochondrial permeability transition pore (mPTP) opening through inhibition of endoplasmic reticulum stress (ERS). Methods: Rat heart tissue-derived cardiac H9c2 myoblast cell line was cultured. Fluorescence images of mitochondrial membrane potential were obtained with confocal microscopy. Western blotting analyzes the ERS marker protein GRP78 expression. Transmission electron microscopy detects the subcellular structure. Results: Exposure of cardiac H9c2 cells to 100 μM 2-DG, the ERS inducer, for 20 min caused a marked decrease in mitochondrial specific tetramethylrhodamine ethyl ester (TMRE) fluorescence. Resveratrol significantly prevented the loss of TMRE fluorescence. Western blotting revealed that resveratrol decreased GRP78 expression. Experiments with transmission electron microscopy revealed that resveratrol prevented 2-DG-induced swelling of endoplasmic reticulum and mitochondrial damages. Conclusions: These data suggest that inhibition of ERS leads to the prevention of mPTP opening. Resveratrol prevents the mPTP opening through inhibition of ERS.

Protective effects of p38 MAPK inhibitor SB202190 against hippocampal apoptosis and spatial learning and memory deficits in a rat model of vascular dementia

Vascular dementia (VaD) is a common age-related neurodegenerative disease resulting from chronic hypoxia. In the present study, we examined the protective effects of p38 MAPK inhibitor SB202190 against hippocampal apoptosis and spatial learning and memory deficits in a chronic hypoperfusion rat model of VaD established by permanent bilateral carotid occlusion (2-VO). Sixty rats were randomly divided into sham-operated, VaD model, and VaD plus SB202190 groups (n = 20/group). After sham/2-VO surgery, rats were administered 0.1% DMSO (sham-operated and VaD groups) or SB202190 by intracerebroventricular injection. One week after inhibitor/vehicle treatment, hippocampal p38 MAPK phosphorylation was higher in the model group than in the SB202190 group (P < 0.01). Compared to the model group, the SB202190 group exhibited significantly shorter escape latencies in the Morris water maze hidden platform trials (P < 0.01) and longer times in the original platform quadrant during probe trials (P < 0.01). The SB202190 group also showed significantly reduced neuronal apoptosis in the hippocampus compared to VaD model rats (P < 0.01) as well as higher (antiapoptotic) Bcl-2 expression and lower (proapoptotic) caspase-3 expression (P < 0.01 for both). In conclusion, blockade of the p38 MAPK signaling pathway by SB202190 following permanent 2-OV reduced apoptosis of hippocampal neurons and rescued spatial learning and memory deficits.

Klotho suppresses cardiomyocyte apoptosis in mice with stress-induced cardiac injury via downregulation of endoplasmic reticulum stress

Cardiomyocyte apoptosis is a common pathological alteration in heart disease which results in systolic dysfunction or sudden death. Klotho is a novel anti-aging hormone. We tested the effects of klotho on cell apoptosis in isoproterenol-treated cardiomyocytes. In BALB/c mice, cardiac injury was induced by subcutaneous injection of isoproterenol (5 mg/kg, for 9 days, s.c.). Klotho (0.01 mg/kg, every other day for 4 days, i.p.) was administered to determine the changes in isoproterenol-induced apoptosis. Mouse heart was harvested at day 2, day 5, and day 9 after isoproterenol injection. Isoproterenol induced cardiac apoptosis and endoplasmic reticulum (ER) stress in a time-dependent manner. However, klotho partly reversed isoproterenol-induced cardiac apoptosis and ER stress. These same effects were observed in cultured cardiomyocytes. Furthermore, the results also showed that SB203580, a p38 inhibitor, and SP600125, a c-Jun NH2-terminal kinase (JNK) inhibitor, reduced cardiomyocyte apoptosis and ER stress, however, klotho suppressed isoproterenol-induced activation of p38 and JNK. Taken together, these results indicated that cardioprotection by klotho was related to the attenuation of ER stress and ER stress-induced apoptosis, at least partly, through suppressing activation of the p38 and JNK pathway.