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

Human neural stem cell secretome relieves endoplasmic reticulum stress-induced apoptosis and improves neuronal functions after traumatic brain injury in a rat model

Neural stem cell secretome (NSC-S) plays an important role in neuroprotection and recovery. Studies have shown that endoplasmic reticulum stress (ER stress) is involved in the progression of traumatic brain injury (TBI) and is a crucial cause of secondary damage and neuronal death after brain injury. Whether NSC-S is engaged in ER stress and ER stress-mediated neuronal apoptosis post-TBI has not been investigated. In the study, the Feeney SD male rat model was established. The results showed that NSC-S treatment significantly improved the behavior of rats with TBI. In addition, NSC-S relieved ER stress in TBI rats and was observed by transmission electron microscopy and western blot. The specific mechanism was further elucidated that restoration was achieved by alleviating the PERK-eIF2α pathway and thus protecting neurons from apoptosis. Notably, the discovery of calumenin (CALU) in NSC-S by liquid chromatography-tandem mass spectrometry (LC-MS/MS/MS) may be related to the protective effect of NSC-S on ER stress in neurons. Also, the mechanism by which it functions may be related to ubiquitination. In summary, NSC-S improved prognosis and ER stress in TBI rats and might be a promising treatment for relieving TBI.

Endoplasmic Reticulum Stress Disrupts Mitochondrial Bioenergetics, Dynamics and Causes Corneal Endothelial Cell Apoptosis

Purpose

Endoplasmic reticulum (ER) and mitochondrial stress are independently associated with corneal endothelial cell (CEnC) loss in many corneal diseases, including Fuchs' endothelial corneal dystrophy (FECD). However, the role of ER stress in mitochondrial dysfunction contributing to CEnC apoptosis is unknown. The purpose of this study is to explore the crosstalk between ER and mitochondrial stress in CEnC.

Methods

Human corneal endothelial cell line (HCEnC-21T) and human corneal endothelial tissues were treated with ER stressor tunicamycin. ER stress-reducing chemical 4-phenyl butyric acid (4-PBA) was used in HCEnC-21T after tunicamycin. Fuchs' corneal endothelial cell line (F35T) was used to determine differential activation of ER stress with respect to HCEnC-21T at the baseline. ER stress, mitochondrial-mediated intrinsic apoptotic, mitochondrial fission, and fusion proteins were determined using immunoblotting and immunohistochemistry. Mitochondrial bioenergetics were assessed by mitochondrial membrane potential (MMP) loss and ATP production at 48 hours after tunicamycin. Mitochondria dynamics (shape, area, perimeter) were also analyzed at 24 hours using transmission electron microscopy.

Results

Treatment of HCEnC-21T cell line with tunicamycin activated three ER stress pathways (PERK-eIF2α-CHOP, IRE1α-XBP1, and ATF6), reduced cell viability, upregulated mitochondrial-mediated intrinsic apoptotic molecules (cleaved caspase 9, caspase 3, PARP, Bax, cytochrome C), downregulated anti-apoptotic Bcl-2 protein, initiated mitochondrial dysfunction by loss of MMP and lowering of ATP production, and caused mitochondrial swelling and fragmentation with increased expression of mitochondrial fission proteins (Fis1 and p-Drp1). Fuchs' CEnC (F35T) cell line also showed activation of the ER stress-related proteins (p-eIF2α, GRP78, CHOP, XBP1) compared to HCEnC-21T at the baseline. The 4-PBA ameliorated cell loss and reduced cleaved caspase 3 and 9, thereby rescuing tunicamycin-induced cell death but not mitochondrial bioenergetics in HCEnC-21T cell line.

Conclusions

Tunicamycin-induced ER stress disrupts mitochondrial bioenegetics, dynamics and contributes to the loss of CEnC viability. This novel study highlights the importance of ER-mitochondria crosstalk and its contribution to CEnCs apoptosis, seen in many corneal diseases, including FECD.

Upregulation of miR-335-5p Contributes to Right Ventricular Remodeling via Calumenin in Pulmonary Arterial Hypertension

Right ventricular (RV) failure determines the prognosis in pulmonary arterial hypertension (PAH), but the underlying mechanism is still unclear. Growing evidence has shown that microRNAs participate in RV remodeling. This study is undertaken to explore the role of miR-335-5p in regulating RV remodeling induced by PAH. Two PAH models were used in the study, including the monocrotaline rat model and hypoxia/su5416 mouse model. miRNA sequencing and RT-qPCR validation identified that miR-335-5p was elevated in the RV of PAH rats. In vitro, miR-335-5p expression was increased after angiotensin II treatment, and miR-335-5p inhibition relieved angiotensin II-induced cardiomyocyte hypertrophy. The luciferase reporter assay showed that calumenin was a target gene for miR-335-5p. Pretreatment with miR-335-5p inhibitors could rescue calumenin downregulation induced by angiotensin II in H9C2 cells. Moreover, intracellular Ca²⁺ concentration and apoptosis were increased after angiotensin II treatment, and miR-335-5p inhibition decreased intracellular Ca²⁺ accumulation and apoptosis. Finally, in vivo miR-335-5p downregulation (antagomir miR-335-5p) attenuated RV remodeling and rescued calumenin downregulation under conditions of hypoxia/su5416 exposure. Our work highlights the role of miR-335-5p and calumenin in RV remodeling and may lead to the development of novel therapeutic strategies for right heart failure.

Chromium [Cr(VI)] Exposure Causes Cytotoxicity of Human Bronchial Epithelial Cells (16-HBE) and Proteomic Alterations

Hexavalent chromium [Cr(VI)] is a common industrial pollutant, and exposure may cause toxic effects in multiple organ systems and carcinogenesis, including lung cancer. However, the toxic effect of Cr(VI) on the respiratory system is poorly understood. In the present study, it was demonstrated that Cr(VI) exposure significantly decreased the viability of human bronchial epithelial cells (16-HBE) in a dose-dependent manner. Flow cytometry demonstrated that Cr(VI) enhanced the transition of 16-HBE cells from G₁ to S phase and arrested S-phase progression. Reverse transcription-quantitative polymerase chain reaction analysis revealed a significant alteration in the expression of apoptosis-associated genes in Cr(VI)-treated 16-HBE cells. In addition, using two-dimensional fluorescence differential gel electrophoresis with mass spectrometry, 15 differentially expressed proteins (1 upregulated and 14 downregulated) were identified in 16-HBE cells with Cr(VI) treatment compared with controls. Functional classification revealed that these differentially expressed proteins were involved in apoptosis, cytoskeletal structure, and energy metabolism. In conclusion, these data suggested that Cr(VI) caused toxic effects in bronchial epithelial cells and the mechanisms may involve the abnormal expression of apoptosis-associated proteins, cytoskeletal proteins, and energy metabolism-associated proteins.

Management of Hypercholesterolemia Through Dietary ß-glucans–Insights From a Zebrafish Model

Consumption of lipid-rich foods can increase the blood cholesterol content. β-glucans have hypocholesterolemic effect. However, subtle changes in their molecular branching can influence bioactivity. Therefore, a comparative investigation of the cholesterol-lowering potential of two β-glucans with different branching patterns and a cholesterol-lowering drug, namely simvastatin was undertaken employing the zebrafish (Danio rerio) model of diet-induced hypercholesterolemia. Fish were allocated to 5 dietary treatments; a control group, a high cholesterol group, two β-glucan groups, and a simvastatin group. We investigated plasma total cholesterol, LDL and HDL cholesterol levels, histological changes in the tissues, and explored intestinal transcriptomic changes induced by the experimental diets. Dietary cholesterol likely caused the suppression of endogenous cholesterol biosynthesis, induced dysfunction of endoplasmic reticulum and mitochondria, and altered the histomorphology of the intestine. The two β-glucans and simvastatin significantly abated the rise in plasma cholesterol levels and restored the expression of specific genes to alleviate the endoplasmic reticulum-related effects induced by the dietary cholesterol. Furthermore, the distinct patterns of transcriptomic changes in the intestine elicited by the oat and microalga β-glucans impacted processes such as fatty acid metabolism, protein catabolic processes, and nuclear division. Oat and microalgal β-glucans also altered the pattern of lipid deposition in the liver. Our study provides insights into the effectiveness of different β-glucans to alleviate dysfunctions in lipid metabolism caused by dietary cholesterol.

Hormone-regulated PKA activity in porcine oviductal epithelial cells

The oviduct is a dynamic organ that suffers changes during the oestrous cycle and modulates gamete and embryo physiology. We analyse the possible existence of Protein kinase A (PKA)-dependent hormone-regulated pathways in porcine ampulla and primary cell cultures by 2D-electrophoresis/Western blot using anti-phospho PKA substrate antibodies. Differential phosphorylation was observed for ten proteins that were identified by mass spectrometry. The results were validated for five of the proteins: Annexin A5, Calumenin, Glyoxalase I and II and Enolase I. Immunofluorescence analyses show that Calumenin, Glyoxalase II and Enolase I change their localisation in the oviductal epithelium through the oestrus cycle. The results demonstrate the existence of PKA hormone-regulated pathways in the ampulla epithelium during the oestrus cycle.

Calumenin-1 Interacts with Climp63 to Cooperatively Determine the Luminal Width and Distribution of Endoplasmic Reticulum Sheets

The ER is composed of distinct structures like tubules, matrices, and sheets, all of which are important for its various functions. However, how these distinct ER structures, especially the perinuclear ER sheets, are formed remains unclear. We report here that the ER membrane protein Climp63 and the ER luminal protein calumenin-1 (Calu1) collaboratively maintain ER sheet morphology. We show that the luminal length of Climp63 is positively correlated with the luminal width of ER sheets. Moreover, the lumen-only mutant of Climp63 dominant-negatively narrows the lumen of ER sheets, demonstrating that Climp63 acts as an ER luminal bridge. We also reveal that Calu1 specifically interacts with Climp63 and antagonizes Climp63 in terms of both ER sheet distribution and luminal width. Together, our data provide insight into how the structure of ER sheets is maintained and regulated.

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Climp63 determines the luminal width of ER sheets

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ER luminal protein Calumenin-1 (Calu1) interacts with Climp63

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Knockout of Calu1 triggers ER sheet accumulation and wider sheet lumen

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Calu1 regulates ER sheet morphology in a Climp63-dependent manner

HSP90 inhibitor 17-AAG prevents apoptosis of cardiomyocytes via miR-93-dependent mitigation of endoplasmic reticulum stress

Heart failure accounts for substantial morbidity and mortality worldwide. Accumulating evidence suggests that aberrant cardiac cell death caused by endoplasmic reticulum stress (ERS) is often associated with structural or functional cardiac abnormalities that lead to insufficient cardiac output. The detailed molecular mechanism underlying the pathological death of cardiomyocytes still remains poorly understood. We found that 17-AAG (tanespimycin), an HSP90 (heat shock protein 90) inhibitor often used to kill cancer cells, could potently inhibit tunicamycin-induced ERS and the downstream nuclear factor kappa B activity in neonatal rat cardiomyocytes, leading to diminished apoptotic signaling and thus enhanced cell survival. Interestingly, the antiapoptotic effect of 17-AAG on cardiomyocytes required normal expression of miR-93, an oncogenic microRNA known to promote cell survival and growth. Our study implicated a new pharmacological role of 17-AAG in supporting the miR-93-associated oncogenic signaling to prevent the pathological death of cardiomyocytes. The results opened opportunities for exploring new strategies in the development of therapeutic agents.

MiR-378 modulates energy imbalance and apoptosis of mitochondria induced by doxorubicin

Doxorubicin (DOX) is an effective anticancer drug, however its clinical application is limited due to its cardiotoxicity. Therefore, understanding the mechanisms of cardiotoxicity induced by DOX is essential. We found that the level of miR-378 was decreased in the hearts of DOX-treated rats. Increasing the expression of miR-378 resulted in a decrease of lactate dehydrogenase (LDH) upon DOX treatment in vitro by targeting lactate dehydrogenase A (LDHA). Furthermore, bioinformatics analysis indicated that cyclophilin A (PPIA), a regulator of apoptosis, is also a direct target gene of miR-378. We confirmed this by Western blot. Our results also showed that the overexpression of miR-378 inhibited the hyperactivation of ER stress signaling induced by DOX. In addition, MiR-378 overexpression was found to protect cardiomyocytes from DOX-induced energy imbalance and apoptosis of mitochondria. These results may allow for a therapeutic approach that overcomes the cardiotoxicity of DOX-based treatments for cancer.

Araloside C Prevents Hypoxia/Reoxygenation-Induced Endoplasmic Reticulum Stress via Increasing Heat Shock Protein 90 in H9c2 Cardiomyocytes

Araloside C (AsC) is a cardioprotective triterpenoid compound that is mainly isolated from Aralia elata. This study aims to determine the effects of AsC on hypoxia-reoxygenation (H/R)-induced apoptosis in H9c2 cardiomyocytes and its underlying mechanisms. Results demonstrated that pretreatment with AsC (12.5 μM) for 12 h significantly suppressed the H/R injury in H9c2 cardiomyocytes, including improving cell viability, attenuating the LDH leakage and preventing cardiomyocyte apoptosis. AsC also inhibited H/R-induced ER stress by reducing the activation of ER stress pathways (PERK/eIF2α and ATF6), and decreasing the expression of ER stress-related apoptotic proteins (CHOP and caspase-12). Moreover, AsC greatly improved the expression level of HSP90 compared with that in the H/R group. The use of HSP90 inhibitor 17-AAG and HSP90 siRNA blocked the above suppression effect of AsC on ER stress-related apoptosis caused by H/R. Taken together, AsC could reduce H/R-induced apoptosis possibly because it attenuates ER stress-dependent apoptotic pathways by increasing HSP90 expression.

Protective effect of miR378* on doxorubicin-induced cardiomyocyte injury via calumenin

Doxorubicin (Dox) is a highly effective antitumor antibiotic, however myocardial toxicity severely limits its use clinically. The pathogenesis of doxorubicin-induced cardiomyopathy is unclear. In Dox cardiomyopathy mice, there is a decline in cardiac function, a change in myocardial pathology and a reduction in miR378* expression. Expression changes in calumenin, an endoplasmic reticulum stress (ERS) chaperone protein and pathway factor, as well as apoptosis, were observed in cardiomyocytes after doxorubicin-induced injury. However, miR378* increased calumenin expression, eased ERS, and reduced cardiomyocyte apoptosis, while, silencing miR378* reduced calumenin expression, aggravated ERS, and increased cardiomyocyte apoptosis. The above results indicate that miR378* alleviates ERS and inhibits the activation of the ERS-mediated apoptosis signaling pathway in cardiomyocytes via regulating calumenin expression, thereby reducing cardiomyocyte apoptosis after doxorubicin-induced injury. Increasing miR378* expression may be a new way to improve cardiac function and quality of life in patients with Dox cardiomyopathy.