Reticulum Stress In Cardiomyocytes Research Articles

Emerging role of melatonin in the alleviation of ischemic heart disease: A comprehensive review

Melatonin, a circardian biomolecule exerts cardioprotective effects through its ability to directly scavenge free radicals and to indirectly act as an antioxidant. It has biological functions such as anti-apoptosis, anti-inflammation, antioxidant activity, mitochondrial protection, and controlling the production of cytokines by target cells. Melatonin also showed blood pressure lowering, normalising lipid profiles, and anti-inflammatory characteristics. Melatonin plays critical roles in averting oxidative stress, enhancing autophagic cell repair, modulating immunological and inflammatory responses, improving mitochondrial function, and reducing endoplasmic reticulum stress in cardiomyocytes. The absence of these cardioprotective properties due to low melatonin levels may be linked to an array of cardiovascular diseases, including ischemic heart disease. As a result, administration of melatonin is anticipated to have a clinically important role in the management of ischemic heart disease; an assertion backed by melatonin's low toxicity and high safety. Therefore, the evidence gathered in this review should provide comprehensive information on melatonin's effect in cardioprotection and, perhaps, contribute to the planning of future experimental studies.

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The cover image is based on the Research Article Tanshinone IIA ameliorates experimental diabetic cardiomyopathy by inhibiting endoplasmic reticulum stress in cardiomyocytes via SIRT1 by Shun Wu et al., https://doi.org/10.1002/ptr.7831.image

Tanshinone IIA ameliorates experimental diabetic cardiomyopathy by inhibiting endoplasmic reticulum stress in cardiomyocytes via SIRT1.

Diabetic cardiomyopathy (DCM) is a common complication in patients with diabetes, and ultimately leads to heart failure. Endoplasmic reticulum stress (ERS) induced by abnormal glycolipid metabolism is a critical factor that affects the occurrence and development of DCM. Additionally, the upregulation/activation of silent information regulation 2 homolog-1 (SIRT1) has been shown to protect against DCM. Tanshinone II A (Tan IIA), the main active component of Salviae miltiorrhizae radix et rhizome (a valuable Chinese medicine), has protective effects against cardiovascular disease and diabetes. However, its role and mechanisms in diabetes-induced cardiac dysfunction remain unclear. Therefore, we explored whether Tan IIA alleviates ERS-mediated DCM via SIRT1 and elucidated the underlying mechanism. The results suggested that Tan IIA alleviated the pathological changes in the hearts of diabetic mice, ameliorated the cytopathological morphology of cardiomyocytes, reduced the cell death rate, and inhibited the expression of ERS-related proteins and mRNA. The SIRT1 agonist inhibited the activities of glucose-regulated protein 78 (GRP78). Furthermore, the opposite results under the SIRT1 inhibitor. SIRT1 knockdown was induced by siRNA-SIRT1 transfection, and the degree of GRP78 acetylation was increased. Cumulatively, Tan IIA ameliorated DCM by inhibiting ERS and upregulating SIRT1 expression.

Deletion of the stress response protein REDD1 prevents impaired cardiac function in diabetic mice

The overwhelming impact of heart failure on morbidity and mortality in obesity and type 2 diabetes requires a deeper understanding of the molecular events that mediate cardiac dysfunction. We recently demonstrated using in vivo and in vitro models of diabetes that upregulation of endoplasmic reticulum stress in cardiomyocytes promoted expression of the stress response protein regulated in development and DNA damage 1 (REDD1). REDD1 has been implicated in diabetes-induced functional deficits in both the retina and kidney; however, a role for REDD1 in diabetes-induced cardiac dysfunction has not been investigated. Thus, we explored the hypothesis that REDD1 contributes to the development of diabetes-induced cardiac dysfunction. To induce diabetes, 6-week old male wild-type and REDD1 knock-out (KO) B6;129 mice were fed a high-fat high-sugar diet (42% kcal fat, 34% sucrose by weight) for 16 weeks; 2 weeks after initiation of the diet, mice were administered low-dose streptozotocin (STZ) for five consecutive days. Non-diabetic control mice were fed a standard rodent diet and received vehicle injections. Mice with a fasting blood glucose level >250mg/dL were defined as diabetic. At 10 weeks of age, transthoracic echocardiogram was evaluated every 2 weeks using a GE Logique small animal echocardiography machine. After 12 weeks of diabetes, left ventricular ejection fraction (EF) was reduced in diabetic wild-type mice as compared to non-diabetic wild-type mice (51.0 +/-9.8% versus 39.5 +/- 5.5%, p = 0.015). Meanwhile, EF in diabetic REDD1 KO mice (47.4 +/- 6.6%) was similar to that observed in non-diabetic REDD1 KO mice (49.6 +/- 6.7%). To investigate a potential cause of the preserved EF in diabetic REDD1 KO mice, tissue homogenates from the left ventricle were examined by PCR analysis. REDD1 mRNA expression in diabetic wild-type mice was enhanced as compared to non-diabetic controls in coordination with increased expression of Tgfb1, as well as expression of the pro-fibrotic genes Fn1, Col1a1, and Col3a1. By contrast, there was no increase in pro-fibrotic mRNA expression in cardiac tissue homogenates from diabetic REDD1 KO mice, as compared to non-diabetic REDD1 KO mice. Overall, the data support a role for REDD1 expression in the development of impaired cardiac function and the pro-fibrotic response of the heart to diabetes. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Circ-SWT1 Ameliorates H2O2-Induced Apoptosis, Oxidative Stress and Endoplasmic Reticulum Stress in Cardiomyocytes via miR-192-5p/SOD2 Axis

Acute myocardial infarction (AMI) is a most serious cardiovascular disease. Increasing findings have indicated that circular RNAs (circRNAs) serve as competent biomarkers in the process of AMI. Herein, our study aimed to probe the functions of circ-SWT1 in cardiomyocyte injury after AMI. H2O2-induced human cardiomyocyte cell line AC16 were used for expression and function analyses. The levels of genes and proteins were detected by qRT-PCR and western blotting. Cell apoptosis was analyzed by flow cytometry and caspase3 activity analysis. The oxidative stress injury was evaluated by detecting the levels of reactive oxygen species (ROS), malondialdehyde and superoxide dismutase (SOD). Western blotting was used to detect the expressions of apoptosis-related markers and endoplasmic reticulum stress (ERS) markers. Dual-luciferase reporter, RIP and pull-down assays were applied to confirm the interaction between miR-192-5p and circ-SWT1 or SOD2. H2O2 treatment significantly decreased circ-SWT1 expression in cardiomyocytes, functionally, ectopic expression of circ-SWT1 attenuated H2O2-triggered apoptosis, oxidative stress and endoplasmic reticulum (ER) stress in cardiomyocytes in vitro. Mechanistically, circ-SWT1 competitively bound to miR-192-5p to relieve the repression of miR-192-5p on its target SOD2. Further rescue experiments showed that miR-192-5p upregulation reversed the inhibitory effects of circ-SWT1 on H2O2-induced cardiomyocyte injury. Moreover, miR-192-5p inhibition protected cardiomyocytes against H2O2-evoked apoptosis, oxidative stress and ER stress, which were abolished by SOD2 silencing. Circ-SWT1 ameliorates H2O2-induced apoptosis, oxidative stress and ER stress in cardiomyocytes via miR-192-5p/SOD2 axis, suggesting the potential involvement of circ-SWT1 in AMI process.

Intermedin protects thapsigargin‑induced endoplasmic reticulum stress in cardiomyocytes by modulating protein kinase A and sarco/endoplasmic reticulum Ca2+‑ATPase.

Intermedin (IMD) is a calcitonin/calcitonin-related peptide that elicits cardioprotective effects in a variety of heart diseases, such as cardiac hypertrophy and heart failure. However, the molecular mechanism of IMD remains unclear. The present study investigated the effects of IMD on neonatal rat ventricular myocytes treated with thapsigargin. The results of the present study demonstrated that thapsigargin induced apoptosis in cardiomyocytes in a dose- and time-dependent manner. Thapsigargin induced endoplasmic reticulum stress, as determined by increased expression levels of 78-kDa glucose-regulated protein, C/EBP-homologous protein and caspase-12, which were dose-dependently attenuated by pretreatment with IMD. In addition, IMD treatment counteracted the thapsigargin-induced suppression of sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) activity and protein expression levels, and cytoplasmic Ca2+ overload. IMD treatment also augmented the phosphorylation of phospholamban, which is a crucial regulator of SERCA. Additionally, treatment with the protein kinase A antagonist H-89 inhibited the IMD-mediated cardioprotective effects, including SERCA activity restoration, anti-Ca2+ overload, endoplasmic reticulum stress inhibition and antiapoptosis effects. In conclusion, the results of the present study suggested that IMD may protect cardiomyocytes against thapsigargin-induced endoplasmic reticulum stress and the associated apoptosis at least partly by activating the protein kinase A/SERCA pathway.

Regulated Inositol‐Requiring Protein 1‐Dependent Decay as a Mechanism of Corin RNA and Protein Deficiency in Advanced Human Systolic Heart Failure

BackgroundThe compensatory actions of the endogenous natriuretic peptide system require adequate processing of natriuretic peptide pro‐hormones into biologically active, carboxyl‐terminal fragments. Natriuretic peptide pro‐peptide processing is accomplished by corin, a transmembrane serine protease expressed by cardiomyocytes. Brain natriuretic peptide (BNP) processing is inadequate in advanced heart failure and is independently associated with adverse outcomes; however, the molecular mechanisms causing impaired BNP processing are not understood. We hypothesized that the development of endoplasmic reticulum stress in cardiomyocytes in advanced heart failure triggers inositol‐requiring protein 1 (IRE1)‐dependent corin mRNA decay, which would favor a molecular substrate favoring impaired natriuretic peptide pro‐peptide processing.Methods and ResultsTwo independent samples of hearts obtained from patients with advanced heart failure at transplant demonstrated that corin RNA was reduced as Atrial natriuretic peptide (ANP)/BNP RNA increased. Increases in spliced X‐box protein 1, a marker for IRE1‐endoribonuclease activity, were associated with decreased corin RNA. Moreover, ≈50% of the hearts demonstrated significant reductions in corin RNA and protein as compared to the nonfailing control sample. In vitro experiments demonstrated that induction of endoplasmic reticulum stress in cultured cardiomyocytes with thapsigargin activated IRE1's endoribonuclease activity and time‐dependent reductions in corin mRNA. In HL‐1 cells, overexpression of IRE1 activated IRE1 endoribonuclease activity and caused corin mRNA decay, whereas IRE1‐RNA interference with shRNA attenuated corin mRNA decay after induction of endoplasmic reticulum stress with thapsigargin. Pre‐treatment of cells with Actinomycin D to inhibit transcription did not alter the magnitude or time course of thapsigargin‐induced corin mRNA decline, supporting the hypothesis that this was the result of IRE1‐mediated corin mRNA degradation.ConclusionsThese data support the hypothesis that endoplasmic reticulum stress‐mediated, IRE1‐dependent targeted corin mRNA decay is a mechanism leading to corin mRNA resulting in corresponding corin protein deficiency may contribute to the pathophysiology of impaired natriuretic peptide pro‐hormone processing in humans processing in humans with advanced systolic heart failure.

Polyamine Depletion Attenuates Isoproterenol-Induced Hypertrophy and Endoplasmic Reticulum Stress in Cardiomyocytes

Background/Aim: Polyamines (putrescine, spermidine and spermine) play an essential role in cell growth, differentiation and apoptosis. Hypertrophy is accompanied by an increase in polyamine synthesis and endoplasmic reticulum stress (ERS) in cardiomyocytes. The present study was undertaken to elucidate the molecular interactions between polyamines, ERS and cardiac hypertrophy. Methods: Myocardial hypertrophy was simulated by incubating cultured neonatal rat cardiomyocytes in 100 nM isoproterenol (ISO). Polyamine deletion was achieved using 0.5 mM difluoromethylornithine (DFMO). Hypertrophy was estimated using cell surface area measurements, total protein concentrations and atrial natriuretic peptide (ANP) gene expression. Apoptosis was measured using flow cytometry and transmission electron microscopy. Expression of ornithine decarboxylase (ODC) and spermidine/spermine N1-acetyltransferase (SSAT) were analyzed via real-time PCR and Western blotting. Protein expression of ERS and apoptosis factors were analyzed using Western blotting. Results: DFMO (0.5 mM and 2 mM) treatments significantly attenuated hypertrophy and apoptosis induced by ISO in cardiomyocytes. DFMO also decreased lactate dehydrogenase (LDH) and malondialdehyde (MDA) level in the culture medium. In addition, DFMO (0.5 mM) down regulated the expression of ODC, glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), cleaved caspase-12, and Bax and up regulated the expression of SSAT and Bcl-2. Finally, these changes were partly reversed by the addition of exogenous putrescine (0.5 mM). Conclusion: The data presented here suggest that polyamine depletion could inhibit cardiac hypertrophy and apoptosis, which is closely related to the ERS pathway.

Abstract 353: Sunitinib Induces Endoplasmic Reticulum Stress in Cardiomyocytes

Introduction: Chemotherapy-induced cardiac toxicities are the main obstacle for effective treatment of cancer, particularly in patients with pre-existing heart disease. This often results in premature termination of cancer treatment. Prominent among these agents is sunitinib (Sutent), which causes cardiac dysfunction in nearly 20% of cancer patients. It has recently been suggested that cardiac microvascular dysfunction, particularly loss of pericyte coverage, underlies sunitinib-induced cardiac dysfunction. However the exact mechanisms of sunitinib-induced cardiotoxicites are still unknown. Results: Neonatal rat ventricular myocytes were treated with increasing concentrations (100nM-5uM) of sunitinib. Irrespective of the dose, there was a significant increase in markers of ER stress (Grp78, Grp 94, Erp72 and phospo/total-eIF2a) after 24 hours of treatment. The ER stress inducer thapsigargin was used as a positive control. Concordant with an increase in ER stress was the activation of mTOR in sunitinib (but not thapsigargin) treated NRVMs, suggesting a possible role of mTOR-mediated proteotoxicity in sunitinib-induced cardiac dysfunction. Protein synthesis, evaluated by 14 C-phenylalanine incorporation into proteins, was moderately elevated in cells treated with sunitinib. Conclusions: In addition to impairment of angiogenesis and pericyte loss, sunitinib induces mTOR activation and ER stress. We propose that the cardiac myocyte secretes paracrine factors that stabilize the cardiac microcirculation. This process is disrupted by sunitinib and ultimately leads to heart failure.

Effects of sarcoplasmic reticulum calcium ATPase 2a overexpression on endoplasmic reticulum stress in cardiomyocytes

To investigate the effects of sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) overexpression on the endoplasmic reticulum stress (ERS). Ventricular cardiomyocytes were obtained from a neonatal rat, cultured, and then randomly divided into 6 groups: normal control group; hypoxia group cultured in an airtight chamber gassed with 95% N(2)/5% CO2 at 37 degrees C for 72 hours so as to induce ERS; tunicamycin group treated with 10 microg/ml tunicamycin so as to induce ERS too; SERCA2a group transfected with recombinant adenovirus expressing the target gene SERCA2a (rAd-SERCA2a); SERCA2a + hypoxia group; and SERCA2a + tunicamycin group. Western blotting was used to detect the protein expression of SERCA2a, and glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP), both the ERS markers. Flow cytometry was used to detect the apoptosis of the cardiomyocytes, and trypan blue staining was used to detect the survival rate of the cardiomyocytes. (1) The GRP78 expression level of the hypoxia group was 5.1 times as high as that of the control group, and the CHOP expression level of the hypoxia group was 2.5 times as high as hat of the control group. The GRP78 expression level of the tunicamycin group was 4.9 times as high as that of the control group, and the CHOP expression level of the tunicamycin group was 3.1 times as high as hat of the control group. SERCA2a overexpression was found to relieve the expression of GRP78 induced by hypoxia and tunicamycin (49.1% and 50.4% decrease respectively), and to inhibit the activation of CHOP (52.7% and 66.1% decrease respectively). (2) In comparison with the hypoxia group, the protein expression levels of GRP78 and CHOP of the SERCA2a overexpression + hypoxia group were significantly lower by 49.1% and 52.7% respectively, the apoptotic rate was significantly lower by 66.0%, and the cardiomyocyte survival rate was significantly higher by 13.4% (all P < 0.05). Compared with the tunicamycin group, the protein expression levels of GRP78 and CHOP of the SERCA2a overexpression + tunicamycin group were significantly lower by 50.4% and 66.1% respectively, the apoptotic rate was significantly lower by 54.0%, and the cardiomyocyte survival rate was significantly higher by 6.7% (all P < 0.05). SERCA2a overexpression attenuates ERS induced by hypoxia or tunicamycin, and protects cardiomyocytes against ERS-mediated cellular injury.