Interplay between Endoplasmic Reticular Stress and Survivin in Colonic Epithelial Cells

Mogroside V reduced the excessive endoplasmic reticulum stress and mitigated the Ulcerative colitis induced by dextran sulfate sodium in mice

Ulcerative colitis (UC) is an idiopathic, chronic inflammatory condition of the colon, characterized by repeated attacks, a lack of effective treatment options, and significant physical and mental health complications for patients. The endoplasmic reticulum (ER) is a vital intracellular organelle in maintaining cellular homeostasis. Endoplasmic reticulum stress (ERS) is induced when the body is exposed to adverse external stimuli. Numerous studies have shown that ERS-induced apoptosis plays a vital role in the pathogenesis of UC. Mogroside V (MV), an active ingredient of Monk fruit, has demonstrated excellent anti-inflammatory and antioxidant effects. In this study, we investigated the therapeutic effects of MV on dextran sulfate sodium (DSS)-induced UC and its potential mechanisms based on ERS. The results showed that MV exerted a protective effect against DSS-induced UC in mice as reflected by reduced DAI scores, increased colon length, reduced histological scores of the colon, and levels of pro-inflammatory cytokines, as well as decreased intestinal permeability. In addition, the expression of ERS pathway including BIP, PERK, eIF2α, ATF4, CHOP, as well as the apoptosis-related protein including Caspase-12, Bcl-2 and Bax, was found to be elevated in UC. However, MV treatment significantly inhibited the UC and reversed the expression of inflammation signaling pathway including ERS and ERS-induced apoptosis. Additionally, the addition of tunicamycin (Tm), an ERS activator, significantly weakened the therapeutic effect of MV on UC in mice. These findings suggest that MV may be a therapeutic agent for the treatment of DSS-induced UC by inhibiting the activation of the ERS-apoptosis pathway, and may provide a novel avenue for the treatment of UC.

CEBPA Overexpression Enhances β-Cell Proliferation and Survival

A commonality between type 1 and type 2 diabetes is the decline in functional β-cell mass. The transcription factor Nkx6.1 regulates β-cell development and is integral for proper β-cell function. We have previously demonstrated that Nkx6.1 depends on c-Fos mediated upregulation and the nuclear hormone receptors Nr4a1 and Nr4a3 to increase β-cell insulin secretion, survival, and replication. Here, we demonstrate that Nkx6.1 overexpression results in upregulation of the bZip transcription factor CEBPA and that CEBPA expression is independent of c-Fos regulation. In turn, CEBPA overexpression is sufficient to enhance INS-1 832/13 β-cell and primary rat islet proliferation. CEBPA overexpression also increases the survival of β-cells treated with thapsigargin. We demonstrate that increased survival in response to ER stress corresponds with changes in expression of various genes involved in the unfolded protein response, including decreased Ire1a expression. These data show that CEBPA is sufficient to enhance functional β-cell mass by increasing β-cell proliferation and modulating the unfolded protein response.

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.

Ascendancy of unfolded protein response over glioblastoma: estimating progression, prognosis and survival

Glioblastoma (GBM) is presented with a poor prognosis. The endoplasmic reticulum stress (ERS) has been implicated as a major contributor to disease progression and chemoresistance in GBM. Triggering ERS by chemical agents or genetic modulations is identified as some of the reasons for regulating gene expression and the pathogenesis of GBM. ERS initiates unfolded protein response (UPR), an integrated system useful in restoring homeostasis or inducing apoptosis. Modulation of UPR might have positive outcomes in GBM treatment as UPR inducers have been shown to alter cell survival and migration. In the current review, we have utilized GSE7806, a publicly available dataset from Gene Expression Omnibus (GEO), to evaluate the genes expressed during 6.5 hr and 18 hr, which can be comparable to the early and late-onset of the disease. Subsequently, we have elucidated the prognosis and survival information whilst the expression of these genes in the GBM was noted in previous studies. This is the first of its kind review summarizing the most recent gene information correlating UPR and GBM.

Dendrobine suppresses endoplasmic reticulum stress-induced apoptosis through upregulating microRNA miR-381-3p to decrease caspase-4

Dendrobine has been reported to reduce blood lipid levels and apoptosis. The present study was designed to observe the effect of dendrobine in a model of ERS using vascular endothelial cells and to reveal the biological mechanisms and pathways responsible for the therapeutic effects of dendrobine on AS. Human umbilical vein endothelial cells (HUVECs) were pre-treated with various concentrations of dendrobine, followed by treatment with tunicamycin (TM) for the establishment of the cell models of ERS. The proliferation and apoptosis of HUVECs were detected by bromodeoxyuridine staining and flow cytometry, respectively. The target binding association was verified through dual luciferase reporter assay. It was found that TM treatment resulted in a low expression of miR-381-3p. Dendrobine treatment not only promoted the proliferation, but also inhibited the apoptosis of HUVECs induced by TM. The reduced expression of 78-kDa glucose-regulated protein, inositol-requiring enzyme 1, caspase-4, C/EBP homologous protein and caspase-3 was also observed following treatment with dendrobine. Dendrobine reduced the apoptosis of endothelial cells in the model of ERS by increasing miR-381-3p expression, and partially restored the cell proliferation level. This effect was significantly reduced after the expression of miR-381-3p was blocked. On the whole, the present study demonstrated that dendrobine upregulated miR-381-3p expression to inhibit apoptosis induced by ERS in HUVECs and this process was found to be mediated by caspase-4. The findings of the present study may provide new insight into the causes of endothelial cell apoptosis during AS and reveal the potent therapeutic effects of dendrobine in AS.

MicroRNA-494 Regulates Endoplasmic Reticulum Stress in Endothelial Cells

Defects in stress responses are important contributors in many chronic conditions including cancer, cardiovascular disease, diabetes, and obesity-driven pathologies like non-alcoholic steatohepatitis (NASH). Specifically, endoplasmic reticulum (ER) stress is linked with these pathologies and control of ER stress can ameliorate tissue damage. MicroRNAs have a critical role in regulating diverse stress responses including ER stress. Here, we show that miR-494 plays a functional role during ER stress. Pharmacological ER stress inducers (tunicamycin (TCN) and thapsigargin) and hyperglycemia robustly increase the expression of miR-494 in vitro. ATF6 impacts the primary miR-494 levels whereas all three ER stress pathways are necessary for the increase in mature miR-494. Surprisingly, miR-494 pretreatment dampens the induction and magnitude of ER stress in response to TCN in endothelial cells and increases cell viability. Conversely, inhibition of miR-494 increases ER stress de novo and amplifies the effects of ER stress inducers. Using Mass Spectrometry (TMT-MS) we identified 23 proteins that are downregulated by both TCN and miR-494 in cultured human umbilical vein endothelial cells. Among these, we found 6 transcripts which harbor a putative miR-494 binding site. We validated the anti-apoptotic gene BIRC5 (survivin) and GINS4 as targets of miR-494 during ER stress. In summary, our data indicates that ER stress driven miR-494 may act in a feedback inhibitory loop to dampen downstream ER stress signaling.

The complex interplay between endoplasmic reticulum stress and the NLRP3 inflammasome: a potential therapeutic target for inflammatory disorders

Inflammation is the result of a complex network of cellular and molecular interactions and mechanisms that facilitate immune protection against intrinsic and extrinsic stimuli, particularly pathogens, to maintain homeostasis and promote tissue healing. However, dysregulation in the immune system elicits excess/abnormal inflammation resulting in unintended tissue damage and causes major inflammatory diseases including asthma, chronic obstructive pulmonary disease, atherosclerosis, inflammatory bowel diseases, sarcoidosis and rheumatoid arthritis. It is now widely accepted that both endoplasmic reticulum (ER) stress and inflammasomes play critical roles in activating inflammatory signalling cascades. Notably, evidence is mounting for the involvement of ER stress in exacerbating inflammasome-induced inflammatory cascades, which may provide a new axis for therapeutic targeting in a range of inflammatory disorders. Here, we comprehensively review the roles, mechanisms and interactions of both ER stress and inflammasomes, as well as their interconnected relationships in inflammatory signalling cascades. We also discuss novel therapeutic strategies that are being developed to treat ER stress- and inflammasome-related inflammatory disorders.

Endogenous Anti-Cancer Candidates in GPCR, ER Stress, and EMT

The majority of cellular responses to external stimuli are mediated by receptors such as G protein-coupled receptors (GPCRs) and systems including endoplasmic reticulum stress (ER stress). Since GPCR signalling is pivotal in numerous malignancies, they are widely targeted by a number of clinical drugs. Cancer cells often negatively modulate GPCRs in order to survive, proliferate and to disseminate. Similarly, numerous branches of the unfolded protein response (UPR) act as pro-survival mediators and are involved in promoting cancer progression via mechanisms such as epithelial to mesenchymal transition (EMT). However, there are a few proteins among these groups which impede deleterious effects by orchestrating the pro-apoptotic phenomenon and paving a therapeutic pathway. The present review exposes and discusses such critical mechanisms and some of the key processes involved in carcinogenesis.

Characterization of a PERK Kinase Inhibitor with Anti-Myeloma Activity

Due to increased immunoglobulin production and uncontrolled proliferation, multiple myeloma (MM) plasma cells develop a phenotype of deregulated unfolded protein response (UPR). The eIF2-alpha kinase 3 [EIF2αK3, protein kinase R (PKR)-like ER kinase (PERK)], the third known sensor of endoplasmic reticulum (ER) stress, is a serine-threonine kinase and, like the other two UPR-related proteins, i.e., IRE1 and ATF6, it is bound to the ER membrane. MM, like other tumors showing uncontrolled protein secretion, is highly dependent to UPR for survival; thus, inhibition of PERK can be an effective strategy to suppress growth of malignant plasma cells. Here, we have used GSK2606414, an ATP-competitive potent PERK inhibitor, and found significant anti-proliferative and apoptotic effects in a panel of MM cell lines. These effects were accompanied by the downregulation of key components of the PERK pathway as well as of other UPR elements. Consistently, PERK gene expression silencing significantly increased cell death in MM cells, highlighting the importance of PERK signaling in MM biology. Moreover, GSK2606414, in combination with the proteasome inhibitor bortezomib, exerted an additive toxic effect in MM cells. Overall, our data suggest that PERK inhibition could represent a novel combinatorial therapeutic approach in MM.

Silica nanoparticles induce unfolded protein reaction mediated apoptosis in spermatocyte cells

With increasing air pollution, silica nanoparticles (SiNPs), as a main inorganic member of PM_2.5, have gained increasing attention to its reproductive toxicity. Most existing studies focused on the acute exposure, while data regarding the chronic effect of SiNPs on reproduction is limited. Therefore, this study was designed to evaluate the chronic toxicity of SiNPs on spermatocyte cells. The cells were continuously exposed to SiNPs for 1, 10, 20 and 30 generations at dose of 5 μg/ml SiNPs for 24 h per generation after attachment. The results showed that with the increasing generations of the exposure, SiNPs decreased the viability of spermatocyte cells, induced apoptosis and increased the level of reactive oxygen species in spermatocyte cells. Moreover, SiNPs increased the protein expression of GRP-78, p-PERK, IRE1α, ATF6 and Cleaved caspase-3 in spermatocyte cells, suggesting that SiNPs improved unfolded protein response (UPR) and apoptosis. The present results indicated that the long-term and low-dose exposure to SiNPs could induce apoptosis by triggering ROS-mediated UPR in spermatocyte cells.

Winnie-APCMin/+ Mice: A Spontaneous Model of Colitis-Associated Colorectal Cancer Combining Genetics and Inflammation

(1) Background: Colorectal cancer (CRC) is among the best examples of the relationship between inflammation and increased cancer risk. (2) Methods: To examine the effects of spontaneous low-grade chronic inflammation on the pathogenesis of CRC, we developed a new murine model of colitis-associated cancer (CAC) by crossing Mucin 2 mutated mice (Winnie) with Apc^Min/+ mice. (3) Results: The resulting Winnie-Apc^Min/+ model combines an inflammatory background with a genetic predisposition to small intestinal polyposis. Winnie-Apc^Min/+ mice show an early occurrence of inflammatory signs and dysplastic lesions in the distal colon with a specific molecular signature. (4) Conclusion: The Winnie-Apc^Min/+ model is a perfect model to demonstrate that chronic inflammation represents a crucial risk factor for the onset and progression of tumoral lesions in individuals genetically predisposed to CRC.

Aldehyde biphenyl chalcones induce immunogenic apoptotic-like cell death and are promising new safe compounds against a wide range of hematologic cancers

Aim: Investigate the apoptotic mechanisms of two new aldehyde biphenyl chalcones on leukemia cells. Materials & methods: From a series of 71 new chalcones, we selected the two most cytotoxic. Results: JA3 and JA7 were cytotoxic not only against hematological malignancies but also against solid tumor and cancer stem cells, yet with no toxicity to normal cells. Moreover, they induced immunogenic apoptotic-like cell death independently of promyelocytic leukemia protein, with extensive mitochondrial damages downstream of endoplasmic reticulum stress. Preventing endoplasmic reticulum stress and the upregulation of proapoptotic machinery inhibited JA3- and JA7-induced cell death. Likewise, blocking receptor Fas protected cells from killing. They increased the antileukemic effect of cytarabine and vincristine and killed leukemic cells collected from patients with different acute leukemia subtypes. Conclusion: JA3 and JA7 represent new promising prototypes for the development of new chemotherapeutics.

Lobetyolin induces apoptosis of colon cancer cells by inhibiting glutamine metabolism

The purpose of the present study was to evaluate the anti‐cancer property of Lobetyolin on colorectal cancer and explore its potential mechanism. Lobetyolin was incubated with HCT‐116 cells in the absence or presence of ASCT2 inhibitor Benser or p53 inhibitor Pifithrin‐α. The levels of glutamine, glutamic acid, α‐ketoglutarate, ATP and GSH were determined to measure the glutamine metabolism. Annexin V‐FITC/PI staining and TUNEL assay were applied to estimate the apoptotic condition. The levels of ASCT2 were examined by RT‐qPCR, Western blot and immunofluorescence staining. The expressions of cleaved‐caspase‐3, caspase‐3, cleaved‐caspase‐7, caspase‐7, cleaved‐PARP, PARP, p53, p21, bax and survivin were detected using Western blot analysis. As a result, the treatment with Lobetyolin effectively induced apoptosis and glutamine metabolism in HCT‐116 cells through ASCT2 signalling. The inhibition of ASCT2 reduced the glutamine‐related biomarkers and augmented the apoptotic process. We further found that the effect of Lobetyolin on HCT‐116 was related to the expressions of p21 and bax, and transportation of p53 to nucleus. The inhibition of p53 by Pifithrin‐α promoted the inhibitory effect of Lobetyolin on ASCT2‐mediated apoptosis. Lobetyolin also exerted anti‐cancer property in nude mice. In conclusion, the present work suggested that Lobetyolin could induce the apoptosis via the inhibition of ASCT2‐mediated glutamine metabolism, which was possibly governed by p53.

Exploring Cellular Stress Response and Chaperones

Since the pioneering discovery of heat shock proteins in Drosophila by Ferruccio Ritossa in 1960s, a long and exciting journey has been undertaken by molecular biologists and researchers worldwide. Not only lower organisms like worms, yeast, amoeba, and flies but also eukaryotes share common cellular response signals to stressful conditions that can arise from the outside but also from the inside. Moreover, extraordinary interplay between nucleus and subcellular organelles, and between different organelles, like mitochondria and the endoplasmic reticulum called mitochondria-associated endoplasmic reticulum membranes (MAMs), are involved in aging and human diseases like obesity, diabetes, inflammation, neurodegeneration, autoimmune diseases, atherosclerosis, and cancer. Actually, we know that to hit abnormal proteostasis and lipid exchanges in the endoplasmic reticulum is crucial to best guide effective therapies or discover new drugs. Indeed, restoration or impairment of endoplasmic reticulum shape and function lead to cellular homeostasis by autophagy or to final death generally by apoptosis or pyroptosis. This Special Issue collects current valuable articles or reviews on cellular stress research and each contribution opens a new window for further studies and hypothesis. I hope that readers interested in this fascinating topic may be stimulated to know more and more.