Endoplasmic reticulum stress as a novel therapeutic target in heart diseases

Endoplasmic reticulum stress-mediated cell death in cardiovascular disease

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

Phenethyl isothiocyanate and irinotecan synergistically induce cell apoptosis in colon cancer HCT 116 cells in vitro

Irinotecan (IRI), an anticancer drug to treat colon cancer patients, causes cytotoxic effects on normal cells. Phenethyl isothiocyanate (PEITC), rich in common cruciferous plants, has anticancer activities (induction of cell apoptosis) in many human cancer cells, including colon cancer cells. However, the anticancer effects of IRI combined with PEITC on human colon cancer cells in vitro were unavailable. Herein, the aim of this study is to focus on the apoptotic effects of the combination of IRI and PEITC on human colon cancer HCT 116 cells in vitro. Propidium iodide (PI) exclusion and Annexin V/PI staining assays showed that IRI combined with PEITC decreased viable cell number and induced higher cell apoptosis than that of IRI or PEITC only in HCT 116 cells. Moreover, combined treatment induced higher levels of reactive oxygen species (ROS) and Ca2+ than that of IRI or PEITC only. Cells pre-treated with N-acetyl-l-cysteine (scavenger of ROS) and then treated with IRI, PEITC, or IRI combined with PEITC showed increased viable cell numbers than that of IRI or PEITC only. IRI combined with PEITC increased higher caspase-3, -8, and -9 activities than that of IRI or PEITC only by flow cytometer assay. IRI combined with PEITC induced higher levels of ER stress-, mitochondria-, and caspase-associated proteins than that of IRI or PEITC treatment only in HCT 116 cells. Based on these observations, PEITC potentiates IRI anticancer activity by promoting cell apoptosis in the human colon HCT 116 cells. Thus, PEITC may be a potential enhancer for IRI in humans as an anticolon cancer drug in the future.

Cardiac performance and heart gene network provide dynamic responses of bay scallop Argopecten irradians irradians exposure to marine heatwaves

The increased frequency of marine heat waves (MHWs) caused by global climate change is predicted to threaten the survival of economic bivalves, therefore having severely adverse effects on local ecological communities and aquaculture production. However, the study of scallops facing MHWs is still scarce, particularly in the scallop Argopecten irradians irradians, which has a significant share of "blue foods" in northern China. In the present study, bay scallop heart was selected to detect its cardiac performance, oxidative impairment and dynamic molecular responses, accompanied by assessing survival variations of individuals in the simulated scenario of MWHs (32 °C) with different time points (0 h, 6 h, 12 h, 24 h, 3 d, 6 d and 10 d). Notably, cardiac indices heart rate (HR), heart amplitude (HA), rate-amplitude product (RAP) and antioxidant enzyme activities superoxide dismutase (SOD) and catalase (CAT) all peaked at 24 h but sharply dropped on 3 d, coinciding with mortality. Transcriptome analysis revealed that the heart actively defended against heat stress at the acute stage (<24 h) via energy supply, misfolded proteins correction and enhanced signal transduction, whereas regulation of the defense response and apoptotic process combined with twice transcription initiation were the dominant responses at the chronic stage (3-10 d). In particular, HSP70 (heat shock protein 70), HSP90 and CALR (calreticulin) in the endoplasmic reticulum were identified as the hub genes (top 5 %) in the HR-associated module via WGCNA (weighted gene co-expression network analysis) trait-module analysis, followed by characterization of their family members and diverse expression patterns under heat exposure. Furthermore, RNAi-mediated knockdown of CALR expression (after 24 h) significantly weakened the thermotolerance of scallops, as evidenced by a drop of 1.31 °C in ABT (Arrhenius break temperature) between the siRNA-injected group and the control group. Our findings elucidated the dynamic molecular responses at the transcriptome level and verified the cardiac functions of CALR in bay scallops confronted with stimulated MHWs.

Exercise sustains the hallmarks of health

Exercise has long been known for its active role in improving physical fitness and sustaining health. Regular moderate-intensity exercise improves all aspects of human health and is widely accepted as a preventative and therapeutic strategy for various diseases. It is well-documented that exercise maintains and restores homeostasis at the organismal, tissue, cellular, and molecular levels to stimulate positive physiological adaptations that consequently protect against various pathological conditions. Here we mainly summarize how moderate-intensity exercise affects the major hallmarks of health, including the integrity of barriers, containment of local perturbations, recycling and turnover, integration of circuitries, rhythmic oscillations, homeostatic resilience, hormetic regulation, as well as repair and regeneration. Furthermore, we summarize the current understanding of the mechanisms responsible for beneficial adaptations in response to exercise. This review aimed at providing a comprehensive summary of the vital biological mechanisms through which moderate-intensity exercise maintains health and opens a window for its application in other health interventions. We hope that continuing investigation in this field will further increase our understanding of the processes involved in the positive role of moderate-intensity exercise and thus get us closer to the identification of new therapeutics that improve quality of life.

Valdecoxib Protects against Cell Apoptosis Induced by Endoplasmic Reticulum Stress via the Inhibition of PERK-ATF4-CHOP Pathway in Experimental Glaucoma

The purpose of this study was to investigate the effects of valdecoxib on the retina in retinal ischemia-reperfusion injury (IRI) and R28 cells following oxygen-glucose deprivation/recovery (OGD/R) injury, as well as the underlying mechanisms. Immunofluorescence and Cell Counting Kit-8 (CCK-8) analyses were used to identify the proper timepoint and concentration of valdecoxib's protective effect on the R28 cells in the OGD/R model. Hematoxylin-eosin (HE) staining and immunofluorescence were used to explore valdecoxib's effect on the retina and retina ganglion cell (RGC) in IRI. Cell apoptosis was determined by a TUNEL Apoptosis Detection Kit and Annexin V-FITC/PI flow cytometry. The expression levels of p-PERK, transcription factor 4 (ATF4), GRP78, CHOP, cleaved caspase 3, bax and bcl-2 were measured by Western blot analyses. The valdecoxib protected the R28 cells from OGD/R injury by decreasing the cell apoptosis rate, and it exerted a protective effect on retinas in I/R injury by inhibiting RGC apoptosis. The valdecoxib pretreatment reversed the expression of p-PERK, ATF4, CHOP, GRP78, cleaved caspase 3 and bax induced by the glaucomatous model. Meanwhile, the CCT020312 reversed the valdecoxib's anti-apoptosis effect by activating PERK-ATF4-CHOP pathway-mediated endoplasmic reticulum (ER) stress. These findings suggest that valdecoxib protects against glaucomatous injury by inhibiting ER stress-induced apoptosis via the inhibition of the PERK-ATF4-CHOP pathway.

Flavonoid Extract from Propolis Provides Cardioprotection following Myocardial Infarction by Activating PPAR-γ

We have previously reported that flavonoid extract from propolis (FP) can improve cardiac function in rats following myocardial infarction (MI). However, the mechanisms responsible for the cardioprotective effects of FP have not been fully elucidated. In the current study, we explored whether FP can reduce inflammatory cytokines and attenuate sympathetic nerve system activity and antiendoplasmic reticulum (ER) stress and whether the cardioprotective effects are related to peroxisome proliferator-activated receptor gamma (PPAR-γ) activation. Sprague Dawley rats were randomly divided into six groups: Sham group received the surgical procedure but no artery was ligated; MI group received ligation of the left anterior descending (LAD) branch of the coronary artery; MI + FP group received FP (12.5 mg/kg/d, intragastrically) seven days prior to LAD ligation; FP group (Sham group + 12.5 mg/kg/d, intragastrically); MI + FP + GW9662 group received FP prior to LAD ligation with the addition of a specific PPAR-γ inhibitor (GW9662), 1 mg/kg/d, orally); and MI + GW9662 group received the PPAR-γ inhibitor and LAD ligation. The results demonstrated that the following inflammatory markers were significantly elevated following MI as compared with expression in sham animals: IL-1β, TNF-α, CRP; markers of sympathetic activation: plasma norepinephrine, epinephrine and GAP43, nerve growth factor, thyroid hormone; and ER stress response markers GRP78 and CHOP. Notably, the above changes were attenuated by FP, and GW9662 was able to alleviate the effect of FP. In conclusion, FP induces a cardioprotective effect following myocardial infarction by activating PPAR-γ, leading to less inflammation, cardiac sympathetic activity, and ER stress.

Estrogen inhibits endoplasmic reticulum stress and ameliorates myocardial ischemia/reperfusion injury in rats by upregulating SERCA2a

Background

The incidence of coronary heart disease (CHD) in premenopausal women is significantly lower than that of men of the same age, suggesting protective roles of estrogen for the cardiovascular system against CHD. This study aimed to confirm the protective effect of estrogen on myocardium during myocardial ischemia/reperfusion (MI/R) injury and explore the underlying mechanisms.

Methods

Neonatal rat cardiomyocytes and Sprague–Dawley rats were used in this study. Different groups were treated by bilateral ovariectomy, 17β-estradiol (E2), adenoviral infection, or siRNA transfection. The expression of sarcoplasmic reticulum Ca²⁺ ATPase pump (SERCA2a) and endoplasmic reticulum (ER) stress-related proteins were measured in each group to examine the effect of different E2 levels and determine the relationship between SERCA2a and ER stress. The cell apoptosis, myocardial infarction size, levels of apoptosis and serum cardiac troponin I, ejection fraction, calcium transient, and morphology changes of the myocardium and ER were examined to verify the effects of E2 on the myocardium.

Results

Bilateral ovariectomy resulted in reduced SERCA2a levels and more severe MI/R injury. E2 treatment increased SERCA2a expression. Both E2 treatment and exogenous SERCA2a overexpression decreased levels of ER stress-related proteins and alleviated myocardial damage. In contrast, SERCA2a knockdown exacerbated ER stress and myocardial damage. Addition of E2 after SERCA2a knockdown did not effectively inhibit ER stress or reduce myocardial injury.

Conclusions

Our data demonstrate that estrogen inhibits ER stress and attenuates MI/R injury by upregulating SERCA2a. These results provide a new potential target for therapeutic intervention and drug discovery in CHD.

Chinese Herbal Medicine Alleviates Myocardial Ischemia/Reperfusion Injury by Regulating Endoplasmic Reticulum Stress

Myocardial ischemia/reperfusion injury is the main cause of increased mortality and disability in cardiovascular diseases. The injury involves many pathological processes, such as oxidative stress, calcium homeostasis imbalance, inflammation, and energy metabolism disorders, and these pathological stimuli can activate endoplasmic reticulum stress. In the early stage of ischemia, endoplasmic reticulum stress alleviates the injury as an adaptive survival response, but the long-term stress on endoplasmic reticulum amplifies oxidative stress, inflammation, and calcium overload to accelerate cell damage and apoptosis. Therefore, regulation of endoplasmic reticulum stress may be a mechanism to improve ischemia/reperfusion injury. Chinese herbal medicine has a long history of clinical application and unique advantages in the treatment of ischemic heart diseases. This review focuses on the effect of Chinese herbal medicine on myocardial ischemia/reperfusion injury from the perspective of regulation of endoplasmic reticulum stress.

Endoplasmic Reticulum-Mitochondria Contacts: A Potential Therapy Target for Cardiovascular Remodeling-Associated Diseases

Cardiovascular remodeling occurs in cardiomyocytes, collagen meshes, and vascular beds in the progress of cardiac insufficiency caused by a variety of cardiac diseases such as chronic ischemic heart disease, chronic overload heart disease, myocarditis, and myocardial infarction. The morphological changes that occur as a result of remodeling are the critical pathological basis for the occurrence and development of serious diseases and also determine morbidity and mortality. Therefore, the inhibition of remodeling is an important approach to prevent and treat heart failure and other related diseases. The endoplasmic reticulum (ER) and mitochondria are tightly linked by ER-mitochondria contacts (ERMCs). ERMCs play a vital role in different signaling pathways and provide a satisfactory structural platform for the ER and mitochondria to interact and maintain the normal function of cells, mainly by involving various cellular life processes such as lipid metabolism, calcium homeostasis, mitochondrial function, ER stress, and autophagy. Studies have shown that abnormal ERMCs may promote the occurrence and development of remodeling and participate in the formation of a variety of cardiovascular remodeling-associated diseases. This review focuses on the structure and function of the ERMCs, and the potential mechanism of ERMCs involved in cardiovascular remodeling, indicating that ERMCs may be a potential target for new therapeutic strategies against cardiovascular remodeling-induced diseases.

Bisphenol A Induces Accelerated Cell Aging in Murine Endothelium

Bisphenol A (BPA) is a widespread endocrine disruptor affecting many organs and systems. Previous work in our laboratory demonstrated that BPA could induce death due to necroptosis in murine aortic endothelial cells (MAECs). This work aims to evaluate the possible involvement of BPA-induced senescence mechanisms in endothelial cells. The β-Gal assays showed interesting differences in cell senescence at relatively low doses (100 nM and 5 µM). Western blots confirmed that proteins involved in senescence mechanisms, p16 and p21, were overexpressed in the presence of BPA. In addition, the UPR (unfolding protein response) system, which is part of the senescent phenotype, was also explored by Western blot and qPCR, confirming the involvement of the PERK-ATF4-CHOP pathway (related to pathological processes). The endothelium of mice treated with BPA showed an evident increase in the expression of the proteins p16, p21, and CHOP, confirming the results observed in cells. Our results demonstrate that oxidative stress induced by BPA leads to UPR activation and senescence since pretreatment with N-acetylcysteine (NAC) in BPA-treated cells reduced the percentage of senescent cells prevented the overexpression of proteins related to BPA-induced senescence and reduced the activation of the UPR system. The results suggest that BPA participates actively in accelerated cell aging mechanisms, affecting the vascular endothelium and promoting cardiovascular diseases.

Adipose-derived stem cells (ADSCs) inhibit the expression of anti-apoptosis proteins through up-regulation of ATF4 on breast cancer cells

Background

While current basic studies indicate adipose-derived stem cells (ADSCs) can promote cell proliferation, clinical trials have shown no significant difference in breast cancer recurrence rates for patients with or without autologous fat grafting (AFG). In this study we attempted to explore the underlying mechanism for these contradictory results.

Methods

ADSCs and umbilical mesenchymal stem cells (UMSCs) were co-cultured with breast cancer cells (MCF-7 and MDA-MB-231), and the cell viability analyzed by CCK-8 cell proliferation assay, TUNEL assay and immunofluorescence assay. In addition, real-time quantitative polymerase chain reaction (RT-qPCR) experiments and Western blot analysis were used to detect the mRNA and protein expression of activating transcription factor 4 (ATF4) and its downstream gene (MCL1 & BCL2), respectively.

Results

Co-cultured ADSCs could promote cell proliferation and cell apoptosis, and up-regulate ATF4 expression both in MCF-7 and MDA-MB-231. While co-cultured UMSCs could only promote cell apoptosis in MCF-7. Interestingly, we found that when co-cultured ADSCs, the expression of MCL1 and BCL2 protein was decreased, even if their mRNA expression was up-regulated both in MCF-7 and MDA-MB-231.

Conclusions

Co-cultured ADSCs can up-regulate ATF4 expression, then interfere with the translation process of MCL1 and BCL2 mRNA and induce cell apoptosis. These data provide insight into the safety characteristics of AFG.

Phosphoproteomic response of cardiac endothelial cells to ischemia and ultrasound

Myocardial infarction and subsequent therapeutic interventions activate numerous intracellular cascades in every constituent cell type of the heart. Endothelial cells produce several protective compounds in response to therapeutic ultrasound, under both normoxic and ischemic conditions. How endothelial cells sense ultrasound and convert it to a beneficial biological response is not known. We adopted a global, unbiased phosphoproteomics approach aimed at understanding how endothelial cells respond to ultrasound. Here, we use primary cardiac endothelial cells to explore the cellular signaling events underlying the response to ischemia-like cellular injury and ultrasound exposure in vitro. Enriched phosphopeptides were analyzed with a high mass accuracy liquid chromatrography (LC) - tandem mass spectrometry (MS/MS) proteomic platform, yielding multiple alterations in both total protein levels and phosphorylation events in response to ischemic injury and ultrasound. Application of pathway algorithms reveals numerous protein networks recruited in response to ultrasound including those regulating RNA splicing, cell-cell interactions and cytoskeletal organization. Our dataset also permits the informatic prediction of potential kinases responsible for the modifications detected. Taken together, our findings begin to reveal the endothelial proteomic response to ultrasound and suggest potential targets for future studies of the protective effects of ultrasound in the ischemic heart.

Pre-clinical Evidence: Berberine as a Promising Cardioprotective Candidate for Myocardial Ischemia/Reperfusion Injury, a Systematic Review, and Meta-Analysis

Objective: Myocardial ischemia/reperfusion (I/R) injury is one of the causes of most cardiomyocyte injuries and deaths. Berberine (BBR) has been suggested a potential to exert protective effects against myocardial I/R injury. This systematic review aims to determine the intrinsic mechanisms of BBR's protective effects in myocardial I/R injury.

Methods: Seven databases were searched for studies performed from inception to July 2020. Methodological quality was assessed by SYRCLE's-RoB tool.

Results: Ten studies including a total of 270 animals were included in this study. The methodology quality scores of the included studies ranged from 5 to 7 points. The meta-analysis we conducted demonstrated that BBR significantly reduced myocardial infarct size and the incidence of ventricular arrhythmia, compared to control groups (P < 0.00001). Cardiac function of animals in the BBR treatment group was also markedly increased (P < 0.00001). The index of myocardial apoptosis and the levels of biomarkers of myocardial infarction (LDH and CK) were also decreased in the BBR treatment groups compared to the control groups (P < 0.00001).

Conclusions: The pre-clinical evidence, according to our study, showed that BBR is a promising therapeutic agent for myocardial I/R injury. However, this conclusion should be further investigated in clinical studies.

Potential Roles of Endoplasmic Reticulum Stress and Cellular Proteins Implicated in Diabesity

The role of the endoplasmic reticulum (ER) has evolved from protein synthesis, processing, and other secretory pathways to forming a foundation for lipid biosynthesis and other metabolic functions. Maintaining ER homeostasis is essential for normal cellular function and survival. An imbalance in the ER implied stressful conditions such as metabolic distress, which activates a protective process called unfolded protein response (UPR). This response is activated through some canonical branches of ER stress, i.e., the protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6 (ATF6). Therefore, chronic hyperglycemia, hyperinsulinemia, increased proinflammatory cytokines, and free fatty acids (FFAs) found in diabesity (a pathophysiological link between obesity and diabetes) could lead to ER stress. However, limited data exist regarding ER stress and its association with diabesity, particularly the implicated proteins and molecular mechanisms. Thus, this review highlights the role of ER stress in relation to some proteins involved in diabesity pathogenesis and provides insight into possible pathways that could serve as novel targets for therapeutic intervention.

Zonisamide, an antiepileptic drug, alleviates diabetic cardiomyopathy by inhibiting endoplasmic reticulum stress

Endoplasmic reticulum stress (ER stress) plays a key role in the development of cardiac hypertrophy and diabetic cardiomyopathy (DCM). Zonisamide (ZNS) was originally developed as an antiepileptic drug. Studies have shown that ZNS suppresses ER stress-induced neuronal cell damage in the experimental models of Parkinson's disease. Herein, we investigated whether ZNS improved DCM by attenuating ER stress-induced apoptosis. C57BL/6J mice were fed with high-fat diet (HFD) and intraperitoneally injected with low-dose streptozotocin (STZ) to induce type 2 diabetes mellitus (T2DM), and then treated with ZNS (40 mg·kg-1·d-1, i.g.) for 16 weeks. We showed that ZNS administration slightly ameliorated the blood glucose levels, but significantly alleviated diabetes-induced cardiac dysfunction and hypertrophy. Furthermore, ZNS administration significantly inhibited the Bax and caspase-3 activity, upregulated Bcl-2 activity, and decreased the proportion of TUNEL-positive cells in heart tissues. We analyzed the hallmarks of ER stress in heart tissues, and revealed that ZNS administration significantly decreased the protein levels of GRP78, XBP-1s, ATF6, PERK, ATF4, and CHOP, and elevated Hrd1 protein. In high glucose (HG)-treated primary cardiomyocytes, application of ZNS (3 μM) significantly alleviated HG-induced cardiomyocyte hypertrophy and apoptosis. ZNS application also suppressed activated ER stress in HG-treated cardiomyocytes. Moreover, preapplication of the specific ER stress inducer tunicamycin (10 ng/mL) eliminated the protective effects of ZNS against HG-induced cardiac hypertrophy and ER stress-mediated apoptosis. Our findings suggest that ZNS improves the cardiac diastolic function in diabetic mice and prevents T2DM-induced cardiac hypertrophy by attenuating ER stress-mediated apoptosis.

Protocatechualdehyde protects oxygen-glucose deprivation/reoxygenation-induced myocardial injury via inhibiting PERK/ATF6α/IRE1α pathway

Endoplasmic reticulum (ER) stress has been considered as a promising strategy in developing novel therapeutic agents for cardiovascular diseases through inhibiting cardiomyocyte apoptosis. Protocatechualdehyde (PCA) is a natural phenolic compound from medicinal plant Salvia miltiorrhiza with cardiomyocyte protection. However, the potential mechanism of PCA on cardiovascular ischemic injury is largely unexplored. Here, we found that PCA exerted markedly anti-apoptotic effect in oxygen-glucose deprivation/reoxygenation (OGD/R)-induced H9c2 cells (Rat embryonic ventricular H9c2 cardiomyocytes), which was detected by 3-(4, 5-dimethyl thiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT), lactate dehydrogenase (LDH), Hoechst 33258 and acridine orange/ethidium bromide (AO/EB) assays. PCA also obviously protected cardiomyocytes in myocardial fibrosis model of mice, which was determined by hematoxylin-eosin (HE) staining and TdT-mediated dUTP Nick-End Labeling (TUNEL) staining. Transcriptomics coupled with bioinformatics analysis revealed a complex pharmacological signaling network especially for PCA-mediated ER stress on cardiomyocytes. Further mechanism study suggested that PCA suppressed ER stress via inhibiting protein kinase R-like ER kinase (PERK), inositol-requiring enzyme1α (IRE1α), and transcription factor 6α (ATF6α) signaling pathway through Western blot, DIOC6 and ER-Tracker Red staining, leading to a protective effect against ER stress-mediated cardiomyocyte apoptosis. Taken together, our observations suggest that PCA is a major component from Salvia miltiorrhiza against cardiovascular ischemic injury by suppressing ER stress-associated PERK, IRE1α and ATF6α signaling pathways.

The importance of autophagy regulation in obstructive sleep apnea

PURPOSE

Autophagy, the self-renewal process of cells, is dependent on lysosomes to degrade damaged organelles and proteins. The increased or damaged level of autophagy is proven to relate to a number of disorders, including metabolic disorders, malignant tumors, pulmonary diseases, and neurodegenerative disorders. This review aims to examine the effects of autophagy on the pathogenic mechanism of obstructive sleep apnea (OSA) in order to guide relevant disease treatment.

METHODS

We conducted a search of the literature using the electronic database, focusing on articles that explored the association between OSA and autophagy.

CONCLUSION

OSA can induced autophagy through hypoxia, oxidative stress, endoplasmic reticulum stress, endothelial dysfunction, miRNA, etc. We propose that the mechanism of the autophagy in patients with OSA should be eclucidated in further studies.

Cardioprotection of pharmacological postconditioning on myocardial ischemia/reperfusion injury

Acute myocardial infarction is associated with high rates of morbidity and mortality and can cause irreversible myocardial damage. Timely reperfusion is critical to limit infarct size and salvage the ischemic myocardium. However, reperfusion may exacerbate lethal tissue injury, a phenomenon known as myocardial ischemia/reperfusion (I/R) injury. Pharmacological postconditioning (PPC), a strategy involving medication administration before or during the early minutes of reperfusion, is more efficient and flexible than preconditioning or ischemic conditioning. Previous studies have shown that various mechanisms are involved in the effects of PPC. In this review, we summarize the relative effects and potential underlying mechanisms of PPC to provide a foundation for future research attempting to develop novel treatments against myocardial I/R injury.

Calreticulin expression in human cardiac myocytes induces ER stress-associated apoptosis

The global burden of heart failure following myocardial ischemia-reperfusion (IR) injury is a growing problem. One pathway that is key to understanding the progression of myocardial infarction and IR injury is the endoplasmic reticulum (ER) stress pathway, which contributes to apoptosis signaling and tissue death. The role of calreticulin in the progression of ER stress remains controversial. We hypothesized that calreticulin induction drives proapoptotic signaling in response to ER stress. We find here that calreticulin is upregulated in human ischemic heart failure cardiac tissue, as well as simulated hypoxia and reoxygenation (H/R) and thapsigargin-mediated ER stress. To test the impact of direct modulation of calreticulin expression on ER stress-induced apoptosis, human cardiac-derived AC16 cells with stable overexpression or silencing of calreticulin were subjected to thapsigargin treatment, and markers of apoptosis were evaluated. It was found that overexpression of calreticulin promotes apoptosis, while a partial knockdown protects against the expression of caspase 12, CHOP, and reduces thapsigargin-driven TUNEL staining. These data shed light on the role that calreticulin plays in apoptosis signaling during ER stress in cardiac cells.

STING is an essential regulator of heart inflammation and fibrosis in mice with pathological cardiac hypertrophy via endoplasmic reticulum (ER) stress

Pathological cardiac hypertrophy is characterized by myocyte enlargement and cardiac dysfunction. However, the pathogenesis for this disease is still poorly understood. Stimulator of interferon genes (STING) could meditate inflammation and immune response in various kinds of diseases. In this work, we demonstrated that STING was critical for pressure overload-induced cardiac hypertrophy. Results showed that STING expression was up-regulated in human and mouse hypertrophic hearts. STING knockout attenuated cardiac hypertrophy induced by aortic banding (AB). The effects of STING deficiency on the improvement of cardiac hypertrophy and dysfunction were associated with the restrained macrophage infiltration, inflammatory response and fibrosis. Moreover, ER stress was detected in hearts of AB-operated mice, as evidenced by the increased expression of phospho-protein kinase RNA-like endoplasmic reticulum kinase (PERK), phospho-eukaryotic initiation factor 2 alpha (eIF2α) and phospho-inositol-requiring kinase (IRE)-1α. Importantly, these proteins were restrained in mice with STING knockout after AB surgery. What's more, angiotensin II (Ang II)-induced STING could be accelerated by ER stress activator, while being markedly abolished by the ER stress inhibitor. We then found that whether co-treated with or without transforming growth factor-beta 1 (TGF-β1), cardiac fibroblasts cultured in the conditional medium (CM) from Ang II-incubated cardiomyocytes with STING knockdown exhibited significantly reduced fibrosis, as displayed by the clearly down-regulated expression of α-SMA, Collagen type I (Col I) and Collagen type III (Col III). Therefore, we defined STING as an important signal contributing to cardiac hypertrophy closely associated with ER stress.

Integrating ER and Mitochondrial Proteostasis in the Healthy and Diseased Heart

The integrity of the proteome in cardiac myocytes is critical for robust heart function. Proteome integrity in all cells is managed by protein homeostasis or proteostasis, which encompasses processes that maintain the balance of protein synthesis, folding, and degradation in ways that allow cells to adapt to conditions that present a potential challenge to viability (1). While there are processes in various cellular locations in cardiac myocytes that contribute to proteostasis, those in the cytosol, mitochondria and endoplasmic reticulum (ER) have dominant roles in maintaining cardiac contractile function. Cytosolic proteostasis has been reviewed elsewhere (2, 3); accordingly, this review focuses on proteostasis in the ER and mitochondria, and how they might influence each other and, thus, impact heart function in the settings of cardiac physiology and disease.

Edaravone Ameliorates Renal Warm Ischemia-Reperfusion Injury by Downregulating Endoplasmic Reticulum Stress in a Rat Resuscitation Model

Background

This study was conducted to explore whether the effect of edaravone (5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol3-one, EDR) can ameliorate renal warm ischemia-reperfusion injury (IRI) by modulating endoplasmic reticulum stress (ERS) and its downstream effector after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) in a rat model.

Methods

The rats (n=10) experienced anaesthesia and intubation followed by no CA inducement were defined as the Sham group. Transoesophageal alternating current stimulation was employed to establish 8 min of CA followed by conventional CPR for a resuscitation model. The rats with successful restoration of spontaneous circulation (ROSC) randomly received EDR (3 mg/kg, EDR group, n=10) or equal volume normal saline solution (the NS group, n=10). At 24 hr after ROSC, serum creatinine (SCR), blood urea nitrogen (BUN) levels, and cystatin-C (Cys-C) levels were determined and the protein level of glucose-regulated protein (GRP78), C/EBP homologous protein (CHOP), extracellular signal-regulated kinase (ERK), phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), Bax/Bcl-2, and caspase-3 were detected by Western blot method.

Results

At 24 hrs after ROSC, SCR, BUN and Cys-C were obviously increased and the proteins expression, including GRP78, CHOP and p-ERK1/2, cleaved-caspase 3 Bax/Bcl-2 ratio, were significantly upregulated in the NS group compared with the Sham group (p<0.05). The remarkable improvement of these adverse outcomes was observed in the EDR group (p<0.05).

Conclusion

In conclusion, we found that EDR ameliorates renal warm IRI by downregulating ERS and its downstream effectors in a rat AKI model evoked by CA/CPR. These data may provide evidence for future therapeutic benefits of EDR against AKI induced by CA/CPR.

Endoplasmic Reticulum Stress Activates Unfolded Protein Response Signaling and Mediates Inflammation, Obesity, and Cardiac Dysfunction: Therapeutic and Molecular Approach

Obesity has been implicated as a risk factor for insulin resistance and cardiovascular diseases (CVDs). Although the association between obesity and CVD is a well-established phenomenon, the precise mechanisms remain incompletely understood. This has led to a relative paucity of therapeutic measures for the prevention and treatment of CVD and associated metabolic disorders. Recent studies have shed light on the pivotal role of prolonged endoplasmic reticulum stress (ERS)-initiated activation of the unfolded protein response (UPR), the ensuing chronic low-grade inflammation, and altered insulin signaling in promoting obesity-compromised cardiovascular system (CVS). In this aspect, potential ways of attenuating ERS-initiated UPR signaling seem a promising avenue for therapeutic interventions. We review intersecting role of obesity-induced ERS, chronic inflammation, insulin resistance, and oxidative stress in the discovery of targeted therapy. Moreover, this review highlights the current progress and strategies on therapeutics being explored in preclinical and clinical research to modulate ERS and UPR signaling.

Intermittent Hypoxia Induces Autophagy to Protect Cardiomyocytes From Endoplasmic Reticulum Stress and Apoptosis

Intermittent hypoxia (IH), characterized as cyclic episodes of short-period hypoxia followed by normoxia, occurs in many physiological and pathophysiological conditions such as pregnancy, athlete, obstructive sleep apnea, and asthma. Hypoxia can induce autophagy, which is activated in response to protein aggregates, in the proteotoxic forms of cardiac diseases. Previous studies suggested that autophagy can protect cells by avoiding accumulation of misfolded proteins, which can be generated in response to ischemia/reperfusion (I/R) injury. The objective of the present study was to determine whether IH-induced autophagy can attenuate endoplasmic reticulum (ER) stress and cell death. In this study, H9c2 cell line, rat primary cultured cardiomyocytes, and C57BL/6 male mice underwent IH with an oscillating O₂ concentration between 4 and 20% every 30 min for 1-4 days in an incubator. The levels of LC3, an autophagy indicator protein and CHOP and GRP78 (ER stress-related proteins) were measured by Western blotting analyses. Our data demonstrated that the autophagy-related proteins were upregulated in days 1-3, while the ER stress-related proteins were downregulated on the second day after IH. Treatment with H₂O₂ (100 μM) for 24 h caused ER stress and increased the level of ER stress-related proteins, and these effects were abolished by pre-treatment with IH condition. In response to the autophagy inhibitor, the level of ER stress-related proteins was upregulated again. Taken together, our data suggested that IH could increase myocardial autophagy as an adaptive response to prevent the ER stress and apoptosis.

Flaccidoxide-13-Acetate-Induced Apoptosis in Human Bladder Cancer Cells is through Activation of p38/JNK, Mitochondrial Dysfunction, and Endoplasmic Reticulum Stress Regulated Pathway

Flaccidoxide-13-acetate, an active compound isolated from cultured-type soft coral Sinularia gibberosa, has been shown to have inhibitory effects against invasion and cell migration of RT4 and T24 human bladder cancer cells. In our study, we used an 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT), colony formation assay, and flow cytometry to determine the mechanisms of the anti-tumor effect of flaccidoxide-13-acetate. The MTT and colony formation assays showed that the cytotoxic effect of flaccidoxide-13-acetate on T24 and RT4 cells was dose-dependent, and the number of colonies formed in the culture was reduced with increasing flaccidoxide-13-acetate concentration. Flow cytometry analysis revealed that flaccidoxide-13-acetate induced late apoptotic events in both cell lines. Additionally, we found that flaccidoxide-13-acetate treatment upregulated the expressions of cleaved caspase 3, cleaved caspase 9, Bax, and Bad, and down-regulated the expressions of Bcl-2, p-Bad, Bcl-x1, and Mcl-1. The results indicated that apoptotic events were mediated by mitochondrial dysfunction via the caspase-dependent pathway. Flaccidoxide-13-acetate also provoked endoplasmic reticulum (ER) stress and led to activation of the PERK-eIF2α-ATF6-CHOP pathway. Moreover, we examined the PI3K/AKT signal pathway, and found that the expressions of phosphorylated PI3K (p-PI3K) and AKT (p-AKT) were decreased with flaccidoxide-13-acetate concentrations. On the other hand, our results showed that the phosphorylated JNK and p38 were obviously activated. The results support the idea that flaccidoxide-13-acetate-induced apoptosis is mediated by mitochondrial dysfunction, ER stress, and activation of both the p38 and JNK pathways, and also relies on inhibition of PI3K/AKT signaling. These findings imply that flaccidoxide-13-acetate has potential in the development of chemotherapeutic agents for human bladder cancer.

VEGF-A promotes angiogenesis after acute myocardial infarction through increasing ROS production and enhancing ER stress-mediated autophagy

Proangiogenesis is generally regarded as an effective approach for treating ischemic heart disease. Vascular endothelial growth factor (VEGF)-A is a strong and essential proangiogenic factor. Reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, and autophagy are implicated in the process of angiogenesis. This study is designed to clarify the regulatory mechanisms underlying VEGF-A, ROS, ER stress, autophagy, and angiogenesis in acute myocardial infarction (AMI). A mouse model of AMI was successfully established by occluding the left anterior descending coronary artery. Compared with the sham-operated mice, the microvessel density, VEGF-A content, ROS production, expression of vascular endothelial cadherin, positive expression of 78 kDa glucose-regulated protein/binding immunoglobulin protein (GRP78/Bip), and LC3 puncta in CD31-positive endothelial cells of the ischemic myocardium were overtly elevated. Moreover, VEGF-A exposure predominantly increased the expression of beclin-1, autophagy-related gene (ATG) 4, ATG5, inositol-requiring enzyme-1 (IRE-1), GRP78/Bip, and LC3-II/LC3-I as well as ROS production in the human umbilical vein endothelial cells (HUVECs) in a dose and time-dependent manner. Both beclin-1 small interfering RNA and 3-methyladenine treatment predominantly mitigated VEGF-A-induced tube formation and migration of HUVECs, but they failed to elicit any notable effect on VEGF-A-increased expression of GRP78/Bip. Tauroursodeoxycholic acid not only obviously abolished VEGF-A-induced increase of IRE-1, GRP78/Bip, beclin-1 expression, and LC3-II/LC3-I, but also negated VEGF-A-induced tube formation and migration of HUVECs. Furthermore, N-acetyl- l-cysteine markedly abrogated VEGF-A-increased ROS production, IRE-1, GRP78/Bip, beclin-1 expression, and LC3-II/LC3-I in the HUVECs. Taken together, our data demonstrated that increased spontaneous production of VEGF-A may induce angiogenesis after AMI through initiating ROS-ER stress-autophagy axis in the vascular endothelial cells.

Origin and Consequences of Necroinflammation

When cells undergo necrotic cell death in either physiological or pathophysiological settings in vivo, they release highly immunogenic intracellular molecules and organelles into the interstitium and thereby represent the strongest known trigger of the immune system. With our increasing understanding of necrosis as a regulated and genetically determined process (RN, regulated necrosis), necrosis and necroinflammation can be pharmacologically prevented. This review discusses our current knowledge about signaling pathways of necrotic cell death as the origin of necroinflammation. Multiple pathways of RN such as necroptosis, ferroptosis, and pyroptosis have been evolutionary conserved most likely because of their differences in immunogenicity. As the consequence of necrosis, however, all necrotic cells release damage associated molecular patterns (DAMPs) that have been extensively investigated over the last two decades. Analysis of necroinflammation allows characterizing specific signatures for each particular pathway of cell death. While all RN-pathways share the release of DAMPs in general, most of them actively regulate the immune system by the additional expression and/or maturation of either pro- or anti-inflammatory cytokines/chemokines. In addition, DAMPs have been demonstrated to modulate the process of regeneration. For the purpose of better understanding of necroinflammation, we introduce a novel classification of DAMPs in this review to help detect the relative contribution of each RN-pathway to certain physiological and pathophysiological conditions.

Salidroside mitigates hypoxia/reoxygenation injury by alleviating endoplasmic reticulum stress‑induced apoptosis in H9c2 cardiomyocytes

Endoplasmic reticulum (ER) stress-induced apoptosis serves a crucial role in the development of myocardial ischemia/reperfusion (I/R) injury. Salidroside is a phenylpropanoid glycoside isolated from Rhodiola rosea L., which is a plant often used in traditional Chinese medicine. It possesses multiple pharmacological actions and protects against myocardial I/R injury in vitro and in vivo. However, it is not yet clear whether ER stress or ER stress-induced apoptosis contributes to the cardioprotective effects of salidroside against myocardial I/R injury. Hence, hypoxia/reoxygenation (H/R)-treated H9c2 cardiomyocytes were used in the current study to mimic myocardium I/R injury in vivo. It was hypothesized that salidroside alleviates ER stress and ER stress-induced apoptosis, thereby reducing H/R injury in H9c2 cells. The results demonstrated that salidroside attenuated H/R-induced H9c2 cardiomyocyte injury, as cell viability was increased, lactate dehydrogenase release was decreased, morphological changes in apoptotic cells were ameliorated and the apoptosis ratio was reduced compared with the H/R group. ER stress was reversed, indicated by the downregulation of glucose regulated protein 78 and C/EBP homologous protein following pretreatment with salidroside. In addition, salidroside attenuated ER stress-induced apoptosis, as the expression of cleaved caspase-12 and pro-apoptotic protein Bcl-2 associated X protein and activity of caspase-3 was decreased, while the expression of anti-apoptotic protein Bcl-2 was increased following pretreatment with salidroside. Furthermore, the results indicated that salidroside decreases the activation of the ER stress-associated signaling pathway, as the expression of phosphorylated protein kinase RNA (PKR)-like ER kinase (p-PERK) and phosphorylated inositol-requiring enzyme-1α (p-IRE1α) proteins were decreased following pretreatment with salidroside. These results demonstrate that salidroside protects against H/R injury via regulation of the PERK and IRE1α pathways, resulting in alleviation of ER stress or ER stress-induced apoptosis in H9c2 cardiomyocytes.

Natural products targeting ER stress pathway for the treatment of cardiovascular diseases

Endoplasmic reticulum (ER) is the main organelle for the synthesis, folding, and processing of secretory and transmembrane proteins. Pathological stimuli including hypoxia, ischaemia, inflammation and oxidative stress interrupt the homeostatic function of ER, leading to accumulation of unfolded proteins, a condition referred to as ER stress. ER stress triggers a complex signalling network referred as the unfolded protein response (UPR). Extensive studies have demonstrated that ER stress plays an important role in the pathogenesis of various cardiovascular diseases such as heart failure, ischemic heart disease and atherosclerosis. The importance of natural products in modern medicine are well recognized and continues to be of interests as a source of novel lead compounds. Natural products targeting components of UPR and reducing ER stress offers an innovative strategic approach to treat cardiovascular diseases. In this review, we discussed several therapeutic interventions using natural products with potential cardiovascular protective properties targeting ER stress signalling pathways.

7-Acetylsinumaximol B Induces Apoptosis and Autophagy in Human Gastric Carcinoma Cells through Mitochondria Dysfunction and Activation of the PERK/eIF2α/ATF4/CHOP Signaling Pathway

The 7-Acetylsinumaximol B (7-AB), a bioactive cembranoid, was originally discovered from aquaculture soft coral Sinularia sandensis. The current study investigated the anti-proliferative property of 7-AB towards the NCI-N87 human gastric cancer cell line. An MTT cell proliferative assay was applied to evaluate cell survival, and immunofluorescence staining and western blotting were employed to analyze the effects of 7-AB on autophagy and apoptosis. Our results showed that 7-AB exerted a concentration-dependent anti-proliferative effect on NCI-N87 cells, and fluorescence staining indicated that the effect was due to the apoptosis induced by 7-AB. In addition, the 7-AB-induced anti-proliferation towards NCI-N87 cells was associated with the release of cytochrome c from mitochondria, activation of pro-apoptotic proteins (such as caspase-3/-9, Bax and Bad), and inhibition of anti-apoptotic proteins (Bcl-2, Bcl-xL, and Mcl-1). The 7-AB treatment also triggered endoplasmic reticulum (ER) stress, leading to activation of the PERK/elF2α/ATF4/CHOP apoptotic pathway. Furthermore, 7-AB initiated autophagy in NCI-N87 cells and induced the expression of autophagy-related proteins, including Atg3, Atg5, Atg7, Atg12, LC3-I, and LC3-II. Taken together, our findings suggested that 7-AB has the potential to be further developed as a useful anti-cancer or adjuvant agent for the treatment of human gastric cancer.

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.

Ghrelin Ameliorates Asthma by Inhibiting Endoplasmic Reticulum Stress

BACKGROUND

This study aimed to confirm the ameliorative effect of ghrelin on asthma and investigate its mechanism.

MATERIALS AND METHODS

The murine model of asthma was induced by ovalbumin (OVA) treatment and assessed by histological pathology and airway responsiveness to methacholine. The total and differential leukocytes were counted. Tumor necrosis factor α, interferon γ, interleukin-5 and interleukin-13 levels in bronchoalveolar lavage fluid were quantified by commercial kits. The protein levels in pulmonary tissues were measured by Western blot analysis.

RESULTS

Ghrelin ameliorated the histological pathology and airway hyperresponsiveness in the OVA-induced asthmatic mouse model. Consistently, OVA-increased total and differential leukocytes and levels of tumor necrosis factor α, interferon γ, interleukin-5 and interleukin-13 in bronchoalveolar lavage fluid were significantly attenuated by ghrelin. Ghrelin prevented the increased protein levels of the endoplasmic reticulum stress markers glucose regulated protein 78 and CCAAT/enhancer binding protein homologous protein and reversed the reduced levels of p-Akt in asthmatic mice.

CONCLUSIONS

Ghrelin might prevent endoplasmic reticulum stress activation by stimulating the Akt signaling pathway, which attenuated inflammation and ameliorated asthma in mice. Ghrelin might be a new target for asthma therapy.

SERCA control of cell death and survival

Intracellular calcium (Ca²⁺⁾ is a critical coordinator of various aspects of cellular physiology. It is increasingly apparent that changes in cellular Ca²⁺ dynamics contribute to the regulation of normal and pathological signal transduction that controls cell growth and survival. Aberrant perturbations in Ca²⁺ homeostasis have been implicated in a range of pathological conditions, such as cardiovascular diseases, diabetes, tumorigenesis and steatosis hepatitis. Intracellular Ca²⁺ concentrations are therefore tightly regulated by a number of Ca²⁺ handling enzymes, proteins, channels and transporters located in the plasma membrane and in Ca²⁺ storage organelles, which work in concert to fine tune a temporally and spatially precise Ca²⁺ signal. Chief amongst them is the sarco/endoplasmic reticulum (SR/ER) Ca²⁺ ATPase pump (SERCA) which actively re-accumulates released Ca²⁺ back into the SR/ER, therefore maintaining Ca²⁺ homeostasis. There are at least 14 different SERCA isoforms encoded by three ATP2A1-3 genes whose expressions are species- and tissue-specific. Altered SERCA expression and activity results in cellular malignancy and induction of ER stress and ER stress-associated apoptosis. The role of SERCA misregulation in the control of apoptosis in various cell types and disease setting with prospective therapeutic implications is the focus of this review. Ca²⁺ is a double edge sword for both life as well as death, and current experimental evidence supports a model in which Ca²⁺ homeostasis and SERCA activity represent a nodal point that controls cell survival. Pharmacological or genetic targeting of this axis constitutes an incredible therapeutic potential to treat different diseases sharing similar biological disorders.

Transcriptional regulation of endothelial-to-mesenchymal transition in cardiac fibrosis: role of myocardin-related transcription factor A and activating transcription factor 3

The etiology of cardiac fibrogenesis is quite diverse, but a common feature is the presence of activated fibroblasts. Experimental evidence suggests that a subset of cardiac fibroblasts is derived via transition of vascular endothelial cells into fibroblasts by endothelial-to-mesenchymal transition (EndMT). During EndMT, endothelial cells lose their endothelial characteristics and acquire a mesenchymal phenotype. Molecular mechanisms and the transcriptional mediators controlling EndMT in heart during development or disease remain relatively undefined. Myocardin-related transcription factor A facilitates the transcription of cytoskeletal genes by serum response factor during fibrosis; therefore, its specific role in cardiac EndMT might be of importance. Activation of activating transcription factor 3 (ATF-3) during cardiac EndMT is speculative, since ATF-3 responds to a transforming growth factor β (TGF-β) stimulus and controls the expression of the primary epithelial-to-mesenchymal transition markers Snail, Slug, and Twist. Although the role of TGF-β in EndMT-mediated cardiac fibrosis has been established, targeting of the TGF-β ligand has not proven to be a viable anti-fibrotic strategy owing to the broad functional importance of this ligand. Thus, targeting of downstream transcriptional mediators may be a useful therapeutic approach in attenuating cardiac fibrosis. Here, we discuss some of the transcription factors that may regulate EndMT-mediated cardiac fibrosis and their involvement in type 2 diabetes.

4-Phenylbutyric Acid Reveals Good Beneficial Effects on Vital Organ Function via Anti-Endoplasmic Reticulum Stress in Septic Rats

OBJECTIVES

Sepsis and septic shock are the common complications in ICUs. Vital organ function disorder contributes a critical role in high mortality after severe sepsis or septic shock, in which endoplasmic reticulum stress plays an important role. Whether anti-endoplasmic reticulum stress with 4-phenylbutyric acid is beneficial to sepsis and the underlying mechanisms are not known.

DESIGN

Laboratory investigation.

SETTING

State Key Laboratory of Trauma, Burns and Combined Injury.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS

Using cecal ligation and puncture-induced septic shock rats, lipopolysaccharide-treated vascular smooth muscle cells, and cardiomyocytes, effects of 4-phenylbutyric acid on vital organ function and the relationship with endoplasmic reticulum stress and endoplasmic reticulum stress-mediated inflammation, apoptosis, and oxidative stress were observed.

MEASUREMENTS AND MAIN RESULTS

Conventional treatment, including fluid resuscitation, vasopressin, and antibiotic, only slightly improved the hemodynamic variable, such as mean arterial blood pressure and cardiac output, and slightly improved the vital organ function and the animal survival of septic shock rats. Supplementation of 4-phenylbutyric acid (5 mg/kg; anti-endoplasmic reticulum stress), especially administered at early stage, significantly improved the hemodynamic variables, vital organ function, such as liver, renal, and intestinal barrier function, and animal survival in septic shock rats. 4-Phenylbutyric acid application inhibited the endoplasmic reticulum stress and endoplasmic reticulum stress-related proteins, such as CCAAT/enhancer-binding protein homologous protein in vital organs, such as heart and superior mesenteric artery after severe sepsis. Further studies showed that 4-phenylbutyric acid inhibited endoplasmic reticulum stress-mediated cytokine release, apoptosis, and oxidative stress via inhibition of nuclear factor-κB, caspase-3 and caspase-9, and increasing glutathione peroxidase and superoxide dismutase expression, respectively.

CONCLUSIONS

Anti-endoplasmic reticulum stress with 4-phenylbutyric acid is beneficial to septic shock. This beneficial effect of 4-phenylbutyric acid is closely related to the inhibition of endoplasmic reticulum stress-mediated oxidative stress, apoptosis, and cytokine release. This finding provides a potential therapeutic measure for clinical critical conditions, such as severe sepsis.

Ibutilide treatment protects against ER stress induced apoptosis by regulating calumenin expression in tunicamycin treated cardiomyocytes

Background

Ibutilide, a class III antiarrhythmic agent has been shown to be cardioprotective in treating atrial fibrillation, promoting cardioconversion and recently this agent has been shown to protect against ER stress induced apoptosis in cardiomyocytes. In this study we begin to identify the mechanism by which ibutilide exerts its cardioprotection in tunicamycin treated cardiomyocytes. We examined ER stress markers including calumenin; a calcium binding ER chaperone protein that has recently been linked to ER stress in cardiomyocytes, in our treated cells.

Methods

To assess the effect of ibutilide we used the well characterized in vitro model of ER stress induced apoptosis in rat neonatal cardiomyocytes (RNC). RNC were treated with tunicamycin and the degree of ER stress was assessed by quantifying mRNA and protein levels of GRP78, GRP94 and calumenin, and examined the extent of apoptosis by assessing the protein levels of caspase-3/9/12, CHOP, ATF6, p-PERK, spliced XBP-1, the ratio of Bax/Bcl-2 and the percentage of deoxynucleotidyl-transferase- mediated dUTP nick end labeling (TUNEL) positive cells.

Results

We demonstrate ibutilide attenuated the up-regulation of ER stress markers GRP78 and GRP94 and rescued the decline in calumenin mRNA and protein levels in tunicamycin treated cardiomyocytes. The up-regulation of apoptotic markers caspase-3, CHOP, ATF6, p-PERK, spliced XBP-1, the ratio of Bax/Bcl-2 and the percentage of TUNEL positive cells were also attenuated after ibutilide treatment while the protein levels of Caspase-9 and Caspase-12 were unaffected.

Conclusions

This study suggests another cardioprotective effect of the antiarrhythmic agent ibutilide whereby pretreatment leads to the attenuation of ER stress induced apoptosis by regulating calumenin expression. This study provides further evidence for the role of calumenin in the cardiomyocyte ER stress response.

Transplantation and Damage-Associated Molecular Patterns (DAMPs)

Upon solid organ transplantation and during cancer immunotherapy, cellular stress responses result in the release of damage-associated molecular patterns (DAMPs). The various cellular stresses have been characterized in detail over the last decades, but a unifying classification based on clinically important aspects is lacking. Here, we provide an in-depth review of the most recent literature along with a unifying concept of the danger/injury model, suggest a classification of DAMPs, and review the recently elaborated mechanisms that result in the emission of such factors. We further point out the differences in DAMP responses including the release following a heat shock pattern, endoplasmic reticulum stress, DNA damage-mediated DAMP release, and discuss the diverse pathways of regulated necrosis in this respect. The understanding of various forms of DAMPs and the consequences of their different release patterns are prerequisite to associate serum markers of cellular stresses with clinical outcomes.

DAMP-Induced Allograft and Tumor Rejection: The Circle Is Closing

The pathophysiological importance of the immunogenicity of damage-associated molecular patterns (DAMPs) has been pinpointed by their identification as triggers of allograft rejection following release from dying cells, such as after ischemia-reperfusion injury. In cancers, however, this strong trigger of a specific immune response gives rise to the success of cancer immunotherapy. Here, we review the recently literature on the pathophysiological importance of DAMP release and discuss the implications of these processes for allograft rejection and cancer immunotherapy, revealing a striking mechanistic overlap. We conclude that these two fields share a common mechanistic basis of regulated necrosis and inflammation, the molecular characterization of which may be helpful for both oncologists and the transplant community.

Aerobic exercise training rescues cardiac protein quality control and blunts endoplasmic reticulum stress in heart failure rats

Cardiac endoplasmic reticulum (ER) stress through accumulation of misfolded proteins plays a pivotal role in cardiovascular diseases. In an attempt to reestablish ER homoeostasis, the unfolded protein response (UPR) is activated. However, if ER stress persists, sustained UPR activation leads to apoptosis. There is no available therapy for ER stress relief. Considering that aerobic exercise training (AET) attenuates oxidative stress, mitochondrial dysfunction and calcium imbalance, it may be a potential strategy to reestablish cardiac ER homoeostasis. We test the hypothesis that AET would attenuate impaired cardiac ER stress after myocardial infarction (MI). Wistar rats underwent to either MI or sham surgeries. Four weeks later, rats underwent to 8 weeks of moderate‐intensity AET. Myocardial infarction rats displayed cardiac dysfunction and lung oedema, suggesting heart failure. Cardiac dysfunction in MI rats was paralleled by increased protein levels of UPR markers (GRP78, DERLIN‐1 and CHOP), accumulation of misfolded and polyubiquitinated proteins, and reduced chymotrypsin‐like proteasome activity. These results suggest an impaired cardiac protein quality control. Aerobic exercise training improved exercise capacity and cardiac function of MI animals. Interestingly, AET blunted MI‐induced ER stress by reducing protein levels of UPR markers, and accumulation of both misfolded and polyubiquinated proteins, which was associated with restored proteasome activity. Taken together, our study provide evidence for AET attenuation of ER stress through the reestablishment of cardiac protein quality control, which contributes to better cardiac function in post‐MI heart failure rats. These results reinforce the importance of AET as primary non‐pharmacological therapy to cardiovascular disease.

4-Phenylbutyric Acid Induces Protection against Pulmonary Arterial Hypertension in Rats

BACKGROUND

Endoplasmic reticulum (ER) stress has been implicated in the pathophysiology of various pulmonary diseases via the activation of the unfolded protein response. However, the role of ER stress in pulmonary arterial hypertension (PAH) remains unclear. The well-known chemical chaperone 4-phenylbutyric acid (4-PBA) inhibits ER stress signaling. We hypothesized that known chemical chaperones, including 4-PBA, would inhibit the activation of ER stress and prevent and/or reverse PAH.

METHODS AND RESULTS

Male Wistar rats were randomly divided into four groups: a normal control group (NORMAL group), a PAH group, and two PAH model plus 4-PBA treatment groups. The latter two groups included rats receiving 4-PBA by gavage each day as a preventive measure (the PRE group, with PBA starting on the day of PAH induction and continuing for 4 weeks) or as a reversal measure (the REV group, with PBA starting on the third week of PAH induction and continuing for 2 weeks). The PAH model was induced by intraperitoneally administering monocrotaline. The mean pulmonary artery pressure and mean right ventricular pressure were lower in the REV and PRE groups than in the NORMAL group. Furthermore, 4-PBA improved pulmonary arterial remodeling and suppressed the expression of ER stress indicators.

CONCLUSION

Our findings indicate that PAH induces ER stress and provokes pulmonary arterial and right ventricular remodeling. Additionally, we show that attenuation of ER stress has the potential to be an effective therapeutic strategy for protecting pulmonary arteries.

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.

Thrombospondins in the transition from myocardial infarction to heart failure

The heart's reaction to ischemic injury from a myocardial infarction involves complex cross-talk between the extra-cellular matrix (ECM) and different cell types within the myocardium. The ECM functions not only as a scaffold where myocytes beat synchronously, but an active signaling environment that regulates the important post-MI responses. The thrombospondins are matricellular proteins that modulate cell--ECM interactions, functioning as "sensors" that mediate outside-in and inside-out signaling. Thrombospondins are highly expressed during embryonic stages, and although their levels decrease during adult life, can be re-expressed in high quantities in response to cardiac stress including myocardial infarction and heart failure. Like a Swiss-army knife, the thrombospondins possess many tools: numerous binding domains that allow them to interact with other elements of the ECM, cell surface receptors, and signaling molecules. It is through these that the thrombospondins function. In the present review, we provide basic as well as clinical evidence linking the thrombospondin proteins with the post myocardial infarction response, including inflammation, fibrotic matrix remodeling, angiogenesis, as well as myocyte hypertrophy, apoptosis, and contractile dysfunction in heart failure. We will describe what is known regarding the intracellular signaling pathways that are involved with these responses, paving the road for future studies identifying these proteins as therapeutic targets for cardiac disease.