The modification and assembly of proteins in the endoplasmic reticulum

Blue light irradiation suppresses oral squamous cell carcinoma through induction of endoplasmic reticulum stress and mitochondrial dysfunction

The therapeutic potential of blue light photobiomodulation in cancer treatment, particularly in inhibiting cell proliferation and promoting cell death, has attracted significant interest. Oral squamous cell carcinoma (OSCC) is a prevalent form of oral cancer, necessitating innovative treatment approaches to improve patient outcomes. In this study, we investigated the effects of 420 nm blue LED light on OSCC and explored the underlying mechanisms. Our results demonstrated that 420 nm blue light effectively reduced OSCC cell viability and migration, and induced G2/M arrest. Moreover, we observed that 420 nm blue light triggered endoplasmic reticulum (ER) stress and mitochondrial dysfunction in OSCC cells, leading to activation of the CHOP signal pathway and alterations in the levels of Bcl-2 and Bax proteins, ultimately promoting cell apoptosis. Additionally, blue light suppressed mitochondrial gene expression, likely due to its damage to mitochondrial DNA. This study highlights the distinct impact of 420 nm blue light on OSCC cells, providing valuable insights into its potential application as a clinical treatment for oral cancer.

Fusaric acid inhibits proliferation and induces apoptosis through triggering endoplasmic reticulum stress in MCF-7 human breast cancer cells

Breast cancer has replaced lung cancer to be the leading cancer in the world. Currently, chemotherapy is still the major method for breast cancer therapy, but its overall effect remains unsatisfactory. Fusaric acid (FSA), a mycotoxin derived from fusarium species, has shown potency against the proliferation of several types of cancer cells, but its effect on breast cancer cells has not been examined. Therefore, we explored the possible effect of FSA on the proliferation of MCF-7 human breast cancer cells and uncovered the underlying mechanism in the present study. Our results showed that FSA has a strong anti-proliferative effect on MCF-7 cells through inducing ROS production, apoptosis and arresting cell cycle at G2/M transition phase. Additionally, FSA triggers endoplasmic reticulum (ER) stress in the cells. Notably, the cell cycle arrest and apoptosis inducing effect of FSA can be attenuated by ER stress inhibitor, tauroursodeoxycholic acid. Our study provide evidence that FSA is a potent proliferation inhibition and apoptosis inducing agent against human breast cancer cells, and the possible mechanism involves the activation of ER stress signaling pathways. Our study may highlight that FSA is promising for the future in vivo study and development of potential agent for breast cancer therapy.

ER Ca2+ overload activates the IRE1α signaling and promotes cell survival

BACKGROUND

Maintaining homeostasis of Ca²⁺ stores in the endoplasmic reticulum (ER) is crucial for proper Ca²⁺ signaling and key cellular functions. Although Ca²⁺ depletion has been known to cause ER stress which in turn activates the unfolded protein response (UPR), how UPR sensors/transducers respond to excess Ca²⁺ when ER stores are overloaded remain largely unclear.

RESULTS

Here, we report for the first time that overloading of ER Ca²⁺ can directly sensitize the IRE1α-XBP1 axis. The overloaded ER Ca²⁺ in TMCO1-deficient cells can cause BiP dissociation from IRE1α, promote the dimerization and stability of the IRE1α protein, and boost IRE1α activation. Intriguingly, attenuation of the over-activated IRE1α-XBP1s signaling by a IRE1α inhibitor can cause a significant cell death in TMCO1-deficient cells.

CONCLUSIONS

Our data establish a causal link between excess Ca²⁺ in ER stores and the selective activation of IRE1α-XBP1 axis, underscoring an unexpected role of overload of ER Ca²⁺ in IRE1α activation and in preventing cell death.

Endoplasmic Reticulum Stress and Cancer: Could Unfolded Protein Response Be a Druggable Target for Cancer Therapy?

Unfolded protein response (UPR) is an adaptive response which is used for re-establishing protein homeostasis, and it is triggered by endoplasmic reticulum (ER) stress. Specific ER proteins mediate UPR activation, after dissociation from chaperone Glucose-Regulated Protein 78 (GRP78). UPR can decrease ER stress, producing an ER adaptive response, block UPR if ER homeostasis is restored, or regulate apoptosis. Some tumour types are linked to ER protein folding machinery disturbance, highlighting how UPR plays a pivotal role in cancer cells to keep malignancy and drug resistance. In this review, we focus on some molecules that have been revealed to target ER stress demonstrating as UPR could be a new target in cancer treatment.

Calcium-Signalling in Human Glaucoma Lamina Cribrosa Myofibroblasts

Glaucoma is one of the most common causes of treatable visual impairment in the developed world, affecting approximately 64 million people worldwide, some of whom will be bilaterally blind from irreversible optic nerve damage. The optic nerve head is a key site of damage in glaucoma where there is fibrosis of the connective tissue in the lamina cribrosa (LC) extracellular matrix. As a ubiquitous second messenger, calcium (Ca²⁺) can interact with various cellular proteins to regulate multiple physiological processes and contribute to a wide range of diseases, including cancer, fibrosis, and glaucoma. Our research has shown evidence of oxidative stress, mitochondrial dysfunction, an elevated expression of Ca²⁺ entry channels, Ca²⁺-dependent pumps and exchangers, and an abnormal rise in cytosolic Ca²⁺ in human glaucomatous LC fibroblast cells. We have evidence that this increase is dependent on Ca²⁺ entry channels located in the plasma membrane, and its release is from internal stores in the endoplasmic reticulum (ER), as well as from the mitochondria. Here, we summarize some of the molecular Ca²⁺-dependent mechanisms related to this abnormal Ca²⁺-signalling in human glaucoma LC cells, with a view toward identifying potential therapeutic targets for ongoing optic neuropathy.

Plant polysaccharides with anti-lung injury effects as a potential therapeutic strategy for COVID-19

When coronavirus disease 2019 (COVID-19) develops into the severe phase, lung injury, acute respiratory distress syndrome, and/or respiratory failure could develop within a few days. As a result of pulmonary tissue injury, pathomorphological changes usually present endothelial dysfunction, inflammatory cell infiltration of the lung interstitium, defective gas exchange, and wall leakage. Consequently, COVID-19 may progress to tremendous lung injury, ongoing lung failure, and death. Exploring the treatment drugs has important implications. Recently, the application of traditional Chinese medicine had better performance in reducing fatalities, relieving symptoms, and curtailing hospitalization. Through constant research and study, plant polysaccharides may emerge as a crucial resource against lung injury with high potency and low side effects. However, the absence of a comprehensive understanding of lung-protective mechanisms impedes further investigation of polysaccharides. In the present article, a comprehensive review of research into plant polysaccharides in the past 5 years was performed. In total, 30 types of polysaccharides from 19 kinds of plants have shown lung-protective effects through the pathological processes of inflammation, oxidative stress, apoptosis, autophagy, epithelial–mesenchymal transition, and immunomodulation by mediating mucin and aquaporins, macrophage, endoplasmic reticulum stress, neutrophil, TGF-β1 pathways, Nrf2 pathway, and other mechanisms. Moreover, the deficiencies of the current studies and the future research direction are also tentatively discussed. This research provides a comprehensive perspective for better understanding the mechanism and development of polysaccharides against lung injury for the treatment of COVID-19.

Interleukin-10 Mitigates Doxorubicin-Induced Endoplasmic Reticulum Stress as Well as Cardiomyopathy

The use of doxorubicin (Dox) in cancer patients carries the risk of cardiotoxicity via an increase in oxidative stress, mitochondrial dysfunction, and disturbed endoplasmic reticulum (ER) homeostasis in cardiomyocytes. The present study explores which of the ER transmembrane sensors is involved in Dox-induced apoptosis and whether interleukin-10 (IL-10) has any mitigating effect. There was a time-related increase in apoptosis in cardiomyocytes exposed to 5.43 µg/mL Dox for 0 to 48 h. Dox treatment for 24 h significantly upregulated glucose-regulated proteins 78 and 94, protein disulfide isomerase, cleavage of activating transcription factor 6α, and X-box binding protein 1. These Dox-induced changes in ER stress proteins as well as apoptosis were blunted by IL-10 (10 ng/mL). In Dox-exposed cardiomyocytes, IL-10 also promoted expression of protein kinase-like endoplasmic reticulum kinase and inositol-requiring kinase 1α, which helped in maintaining ER homeostasis. Additionally, under Dox-treatment, IL-10 downregulated caspase-12 activation as well as phosphorylation of c-JUN NH2-terminal kinase, thereby promoting cardiomyocyte survival. IL-10 was able to reduce the overexpression of mitochondrial apoptotic proteins caspase-3 as well as Bax, which were upregulated upon Dox treatment. Thus, a reduction in Dox-induced ER stress as well as apoptosis through IL-10 may provide a significant benefit in improving cardiac function.

Homo-oligomerization of the human adenosine A2A receptor is driven by the intrinsically disordered C-terminus

G protein-coupled receptors (GPCRs) have long been shown to exist as oligomers with functional properties distinct from those of the monomeric counterparts, but the driving factors of oligomerization remain relatively unexplored. Herein, we focus on the human adenosine A2A receptor (A2AR), a model GPCR that forms oligomers both in vitro and in vivo. Combining experimental and computational approaches, we discover that the intrinsically disordered C-terminus of A2AR drives receptor homo-oligomerization. The formation of A2AR oligomers declines progressively with the shortening of the C-terminus. Multiple interaction types are responsible for A2AR oligomerization, including disulfide linkages, hydrogen bonds, electrostatic interactions, and hydrophobic interactions. These interactions are enhanced by depletion interactions, giving rise to a tunable network of bonds that allow A2AR oligomers to adopt multiple interfaces. This study uncovers the disordered C-terminus as a prominent driving factor for the oligomerization of a GPCR, offering important insight into the effect of C-terminus modification on receptor oligomerization of A2AR and other GPCRs reconstituted in vitro for biophysical studies.

Unfolded protein response during cardiovascular disorders: a tilt towards pro-survival and cellular homeostasis

The endoplasmic reticulum (ER) is an organelle that orchestrates the production and proper assembly of an extensive types of secretory and membrane proteins. Endoplasmic reticulum stress is conventionally related to prolonged disruption in the protein folding machinery resulting in the accumulation of unfolded proteins in the ER. This disruption is often manifested due to oxidative stress, Ca²⁺ leakage, iron imbalance, disease conditions which in turn hampers the cellular homeostasis and induces cellular apoptosis. A mild ER stress is often reverted back to normal. However, cells retaliate to acute ER stress by activating the unfolded protein response (UPR) which comprises three signaling pathways, Activating transcription factor 6 (ATF6), inositol requiring enzyme 1 alpha (IRE1α), and protein kinase RNA-activated-like ER kinase (PERK). The UPR response participates in both protective and pro-apoptotic responses and not much is known about the mechanistic aspects of the switch from pro-survival to pro-apoptosis. When ER stress outpaces UPR response then cell apoptosis prevails which often leads to the development of various diseases including cardiomyopathies. Therefore, it is important to identify molecules that modulate the UPR that may serve as promising tools towards effective treatment of cardiovascular diseases. In this review, we elucidated the latest advances in construing the contribution imparted by the three arms of UPR to combat the adverse environment in the ER to restore cellular homeostasis during cardiomyopathies. We also summarized the various therapeutic agents that plays crucial role in tilting the UPR response towards pro-survival.

Dietary taurine supplementation ameliorates muscle loss in chronic heat stressed broilers via suppressing the perk signaling and reversing endoplasmic reticulum-stress-induced apoptosis

BACKGROUND

Heat stress seriously affects animal health and induces enormous financial losses in poultry production. Exploring the appropriate means for ameliorating unfavorable effects caused by heat stress is essential. We investigated whether taurine supplementation could attenuate breast muscle loss in chronic heat-stressed broilers, as well as its mechanism. We designed three groups: a normal control group (22 °C), a heat stress group (32 °C) and a taurine treatment group (32 °C, basal diet + 5 g·kg^-1 taurine).

RESULTS

We found that taurine significantly moderated the decreases of breast muscle mass and yield, as well as the increases of serum aspartate aminotransferase activity and serum urine acid level in chronic heat-stressed broilers. Additionally, supplementary taurine significantly alleviated elevations of the cytoplasm Ca²⁺ concentration, protein expressions of GRP78 and p-PERK, mRNA expressions of Ca²⁺ channels (RyR1, IP3R3) and endoplasmic reticulum (ER) stress factors (GRP78, GRP94, PERK, EIF2α, ATF4, IRE1, XBP1, ATF6 and CHOP), apoptosis (Caspase-3 and TUNEL), protein catabolism, and the reduction of taurine transporter (TauT) mRNA expression in the breast muscle induced by chronic heat stress.

CONCLUSION

Supplementary taurine could attenuate chronic heat stress-induced breast muscle loss via reversing ER stress-induced apoptosis and suppressing protein catabolism. © 2020 Society of Chemical Industry.

Endoplasmic reticulum stress, degeneration of pancreatic islet β-cells, and therapeutic modulation of the unfolded protein response in diabetes

Background

Myriad challenges to the proper folding and structural maturation of secretory pathway client proteins in the endoplasmic reticulum (ER) — a condition referred to as “ER stress” — activate intracellular signaling pathways termed the unfolded protein response (UPR).

Scope of review

Through executing transcriptional and translational programs the UPR restores homeostasis in those cells experiencing manageable levels of ER stress. But the UPR also actively triggers cell degeneration and apoptosis in those cells that are encountering ER stress levels that exceed irremediable thresholds. Thus, UPR outputs are “double-edged”. In pancreatic islet β-cells, numerous genetic mutations affecting the balance between these opposing UPR functions cause diabetes mellitus in both rodents and humans, amply demonstrating the principle that the UPR is critical for the proper functioning and survival of the cell.

Major conclusions

Specifically, we have found that the UPR master regulator IRE1α kinase/endoribonuclease (RNase) triggers apoptosis, β-cell degeneration, and diabetes, when ER stress reaches critical levels. Based on these mechanistic findings, we find that novel small molecule compounds that inhibit IRE1α during such “terminal” UPR signaling can spare ER stressed β-cells from death, perhaps affording future opportunities to test new drug candidates for disease modification in patients suffering from diabetes.

MFN2 Plays a Distinct Role from MFN1 in Regulating Spermatogonial Differentiation

Although mitochondrial morphology is well-known for its role in cellular homeostasis, there is surprisingly little knowledge on whether mitochondrial remodeling is required for postnatal germ cell development. In this study, we investigated the functions of MFN1 and MFN2, two GTPases in mitochondrial fusion, during early spermatogenesis. We observed increased MFN expressions along with increased mitochondrial and endoplasmic reticulum (ER) activities during spermatogonial differentiation. Deletion of either Mfn led to DNA oxidation and apoptosis specifically in differentiating spermatogonia and spermatocytes, which in turn caused male infertility. We further found MFN2 regulated spermatogenesis by modulating both mitochondrial and ER functions, a mechanism distinct from that of MFN1. Defects of germ cell development in MFN2 mutants were corrected by MFN2 at either mitochondria or ER but not by MFN1. Our study thus reveals an essential requirement of MFN-mediated mitochondrial and ER coordination in spermatogenesis, providing critical insights into mitochondrial determinants of male fertility.

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Mitochondrial and ER activities increase during spermatogonial differentiation

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Mfn deletions specifically impair differentiating spermatogonia and spermatocytes

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MFN2 impacts male fertility via regulating mitochondrial fusion and ER homeostasis

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MFN2 functions non-redundantly from MFN1 in spermatogenesis

The impact of proteostasis dysfunction secondary to environmental and genetic causes on neurodegenerative diseases progression and potential therapeutic intervention

Aggregation of particular proteins in the form of inclusion bodies or plaques followed by neuronal death is a hallmark of neurodegenerative proteopathies such as primary Parkinsonism, Alzheimer's disease, Lou Gehrig's disease, and Huntington's chorea. Complex polygenic and environmental factors implicated in these proteopathies. Accumulation of proteins in these disorders indicates a substantial disruption in protein homeostasis (proteostasis). Proteostasis or cellular proteome homeostasis is attained by the synchronization of a group of cellular mechanisms called the proteostasis network (PN), which is responsible for the stability of the proteome and achieves the equilibrium between synthesis, folding, and degradation of proteins. In this review, we will discuss the different types of PN and the impact of PN component dysfunction on the four major neurodegenerative diseases mentioned earlier. Graphical abstract.

OsPDR2 mediates the regulation on the development response and maintenance of Pi homeostasis in rice

Inorganic orthophosphate (Pi), a major form of essential macronutrient phosphorus (P), is available in rhizosphere for acquisition and assimilation by plants. However, the limited availability of Pi in soils affects the growth and development of plants. In Arabidopsis thaliana (Arabidopsis), Phosphate Deficiency Response2 (AtPDR2), interacts genetically with Low Phosphate Root1 (AtLPR1) in the endoplasmic reticulum (ER) and plays a key role in the inhibition of primary root growth (PRG) during Pi deficiency. However, the role of OsPDR2, the homolog of AtPDR2, either in roots response to Pi deficiency and/or in growth and development has not been elucidated as yet. Therefore, qRT-PCR was employed to determine the spatiotemporal effects and the availability of Pi on the expression of OsPDR2. OsPDR2 showed variable levels of relative expression pattern in vegetative and/or reproductive tissues analyzed at different stages of growth and development (5-17 weeks). Transient expression analysis revealed its subcellular localization to the ER. Further, the reverse genetics approach was employed for determining the function of OsPDR2 by generating RNAi lines (Ri2, Ri9, and Ri18). The study revealed significant inhibitory effects of RNAi-mediated suppression of OsPDR2 on the development of root, male reproductive traits, and yield. Moreover, ³²P isotope labeling and split-root experiments under different Pi regime with RNAi lines revealed the function of OsPDR2 in regulating homeostasis of Pi.

Pathological consequences of the unfolded protein response and downstream protein disulphide isomerases in pulmonary viral infection and disease

Protein folding within the endoplasmic reticulum (ER) exists in a delicate balance; perturbations of this balance can overload the folding capacity of the ER and disruptions of ER homoeostasis is implicated in numerous diseases. The unfolded protein response (UPR), a complex adaptive stress response, attempts to restore normal proteostasis, in part, through the up-regulation of various foldases and chaperone proteins including redox-active protein disulphide isomerases (PDIs). There are currently over 20 members of the PDI family each consisting of varying numbers of thioredoxin-like domains which, generally, assist in oxidative folding and disulphide bond rearrangement of peptides. While there is a large amount of redundancy in client proteins of the various PDIs, the size of the family would indicate more nuanced roles for the individual PDIs. However, the role of individual PDIs in disease pathogenesis remains uncertain. The following review briefly discusses recent findings of ER stress, the UPR and the role of individual PDIs in various respiratory disease states.

A Role for Endoplasmic Reticulum Stress in Intracerebral Hemorrhage

The endoplasmic reticulum (ER) is an intracellular organelle that performs multiple functions, such as lipid biosynthesis, protein folding, and maintaining intracellular calcium homeostasis. Thus, conditions wherein the ER is unable to fold proteins is defined as ER stress, and an inbuilt quality control mechanism, called the unfolded protein response (UPR), is activated during ER stress, which serves as a recovery system that inhibits protein synthesis. Further, based on the severity of ER stress, the response could involve both proapoptotic and antiapoptotic phases. Intracerebral hemorrhage (ICH) is the second most common subtype of cerebral stroke and many lines of evidence have suggested a role for the ER in major neurological disorders. The injury mechanism during ICH includes hematoma formation, which in turn leads to inflammation, elevated intracranial pressure, and edema. A proper understanding of the injury mechanism(s) is required to effectively treat ICH and closing the gap between our current understanding of ER stress mechanisms and ICH injury can lead to valuable advances in the clinical management of ICH.

Modification of lung endoplasmic reticulum genes expression and NF-kB protein levels in obese ovalbumin-sensitized male and female rats

AIMS

Previous studies showed a close relationship between obesity and asthma. In this study, we investigated the expression of endoplasmic reticulum (ER) stress genes in the lung tissue of obese ovalbumin (OVA)-sensitized male and female rats.

MAIN METHODS

The rats were divided into eight groups (n = 5 per group) as follows: female and male rats fed with normal diet (FND and MND, respectively), female and male OVA-sensitized rats fed with normal diet (F-OND and M-OND, respectively), female and male rats fed with high-fat diet (F-HFD and M-HFD, respectively), female and male OVA-sensitized rats fed with high-fat diet (F-OHFD and M-OHFD, respectively). All rats were fed with a high-fat diet or standard pelts for 8 weeks, and for another 4 weeks, they were sensitized by OVA or saline. At the end of the study, lung tissue NF-kB protein level was assessed, and ER stress markers genes expression was determined by Real Time-PCR.

KEY FINDING

OVA-sensitization and diet-induced obesity caused the curve of methacholine concentration-response to shift to the left. In addition, the results indicated that the EC50 (the effective concentration of methacholine generating 50% of peak response) in F-OHFD rats was statistically lower than that of the M-OHFD group (p < 0.05). Moreover, the results showed that diet-induced obesity increased the expression of ATF4, ATF6, GRP78, XBP-1, and CHOP as well as the protein level of NF-kB in this experimental model of asthma, markedly in the F-OHFD group.

SIGNIFICANCE

The results suggest that ER stress may be involved in the pathogenesis of asthma observed in obese OVA-sensitized rats, especially in the female animals.

Exposure to etoxazole induces mitochondria-mediated apoptosis in porcine trophectoderm and uterine luminal epithelial cells

Etoxazole is an organofluorine insecticide widely used in agriculture. Exposure to insecticides is a serious environmental problem owing to their cytotoxic effects in humans and animals. Reproductive toxicity of various organofluorine insecticides have been shown in previous studies. However, few studies have evaluated the toxicity of etoxazole in mammals. We aimed to examine the toxic effects of etoxazole in porcine trophectoderm (pTr) and uterine luminal epithelial (pLE) cells. To estimate the effects of etoxazole, we conducted assays after treatment with multiple concentration of etoxazole (0, 2, 4, 6 and 9 μM) to pTr and pLE cells for 0-72 h. Etoxazole decreased the cell proliferation, viability, and migration of pTr and pLE cells. Further, etoxazole induced apoptosis via cell cycle arrest and disruption of mitochondrial membrane potential. We also found that pro-apoptotic proteins and endoplasmic reticulum (ER) stress-response proteins were activated in response to etoxazole. Finally, we observed that etoxazole altered the PI3K/AKT and MAPK signaling pathways and the mRNA expression of genes associated with implantation. Collectively, these results suggest that etoxazole disrupts normal cellular physiology and might cause early implantation failure.

Endoplasmic reticulum stress enhances the antigen-specific T cell immune responses and therapeutic antitumor effects generated by therapeutic HPV vaccines

BACKGROUND

Endoplasmic reticulum stress has a profound effect on cancer cell proliferation and survival, and also has the capacity to activate cells of the adaptive immune system. Multimodal treatment methods that utilize and combine conventional cancer therapies with antigen-specific immunotherapies have emerged as promising approaches for the treatment and control of cancer. However, it is not well known whether endoplasmic reticulum stress-inducing agents can influence the efficacy of tumor antigen-targeting vaccines.

METHODS

In the past, we developed a therapeutic human papillomavirus (HPV) DNA vaccine that encodes for calreticulin (CRT) linked to the HPV16 E7 antigen (CRT/E7). In this study, we utilize the CRT/E7 and further encode for an endoplasmic reticulum (ER) stress-inducing agent, 3-bromopyruvate (3-BrPA), in a preclinical model, by harnessing its potential to enhance HPV16 E7-specific CD8+ T cell immune responses as well as antitumor effects against E7-expressing tumors (TC-1 cells). E7-specific CD8+ T cells were added to evaluate the cytotoxicity of luciferase-expressing TC-1 tumor cells treated with 3-BrPA in vitro, as measured with an IVIS Luminescence Imaging System. We also determined the levels of ER stress markers in 3-BrPA-treated TC-1 cells. TC-1 tumor-bearing mice were treated with either 3-BrPA (10 mg/kg, intraperitoneal injection) and/or CRT/E7 DNA vaccine (30 μg/mouse).

RESULTS

Treatment of E7-expressing TC-1 tumor cells with 3-BrPA induced significantly higher in vitro cytotoxicity and resulted in upregulation of endoplasmic reticulum stress markers (CHOP and GRP78). More importantly, combination treatment of 3-BrPA and the CRT/E7 DNA vaccine led to improved antigen-specific CD8+ T cell immune responses as well as therapeutic antitumor effects in TC-1 tumor-bearing mice.

CONCLUSIONS

Our data indicate that 3-BrPA can enhance therapeutic HPV vaccine potency in generating improved antigen-specific immune responses and antitumor effects. These findings have important implications for future clinical translation and provide novel strategies for the treatment of HPV-associated diseases.

Contrast Induced Acute Kidney Injury and Direct Cytotoxicity of Iodinated Radiocontrast Media on Renal Proximal Tubule Cells

The administration of intravenous iodinated radiocontrast media (RCM) to visualize internal structures during diagnostic procedures has increased exponentially since their first use in 1928. A serious side effect of RCM exposure is contrast-induced acute kidney injury (CI-AKI), which is defined as an abrupt and prolonged decline in renal function occurring 48-72 hours after injection. Multiple attempts have been made to decrease the toxicity of RCM by altering ionic strength and osmolarity, yet there is little evidence to substantiate that a specific RCM is superior in avoiding CI-AKI. RCM-associated kidney dysfunction is largely attributed to alterations in renal hemodynamics, specifically renal vasoconstriction; however, numerous studies indicate direct cytotoxicity as a source of epithelial damage. Exposure of in vitro renal proximal tubule cells to RCM has been shown to affect proximal tubule epithelium in the following manner: 1) changes to cellular morphology in the form of vacuolization; 2) increased production of reactive oxygen species, resulting in oxidative stress; 3) mitochondrial dysfunction, resulting in decreased efficiency of the electron transport chain and ATP production; 4) perturbation of the protein folding capacity of the endoplasmic reticulum (ER) (activating the unfolded protein response and inducing ER stress); and 5) decreased activity of cell survival kinases. The present review focuses on the direct cytotoxicity of RCM on proximal tubule cells in the absence of in vivo complications, such as alterations in renal hemodynamics or cytokine influence.

Ethyl Acetate Extract of Scindapsus cf. hederaceus Exerts the Inhibitory Bioactivity on Human Non-Small Cell Lung Cancer Cells through Modulating ER Stress

Unfolded protein response (UPR) is a cytoprotective mechanism that alleviates the protein-folding burden in eukaryotic organisms. Moderate activation of UPR is required for maintaining endoplasmic reticulum (ER) homeostasis and profoundly contributes to tumorigenesis. Defects in UPR signaling are implicated in the attenuation of various malignant phenotypes including cell proliferation, migration, and invasion, as well as angiogenesis. This suggests UPR as a promising target in cancer therapy. The pharmacological effects of the plant Scindapsus cf. hederaceus on human cancer cell lines is not understood. In this study, we identified an ethyl acetate extract from Scindapsus cf. hederaceus (SH-EAE), which markedly altered the protein expression of UPR-related genes in human non-small cell lung cancer (NSCLC) cells. Treatment with the SH-EAE led to the dose-dependent suppression of colony forming ability of both H1299 and H460 cells, but not markedly in normal bronchial epithelial BEAS-2B cells. SH-EAE treatment also attenuated the migration and invasion ability of H1299 and H460 cells. Moreover, SH-EAE strikingly suppressed the protein expression of two ER stress sensors, including inositol requiring enzyme-1α (IRE-1α) and protein kinase R-like ER kinase (PERK), and antagonized the induction of C/EBP homologous protein (CHOP) expression by thapsigargin, an ER stress inducer. SH-EAE induced the formation of massive vacuoles which are probably derived from ER. Importantly, SH-EAE impaired the formation of intersegmental vessels (ISV) in zebrafish larvae, an index of angiogenesis, but had no apparent effect on the rate of larval development. Together, our findings demonstrate, for the first time, that the ability of SH-EAE specifically targets the two sensors of UPR, with significant anti-proliferation and anti-migration activities as a crude extract in human NSCLC cells. Our finding also indicates potential applications of SH-EAE in preventing UPR activation in response to Tg-induced ER stress. We suggest that SH-EAE attenuates UPR adaptive pathways for rendering the NSCLC cells intolerant to ER stress.

Sputum proteomics and airway cell transcripts of current and ex-smokers with severe asthma in U-BIOPRED: an exploratory analysis

Severe asthma patients with a significant smoking history have airflow obstruction with reported neutrophilia. We hypothesise that multi-omic analysis will enable the definition of smoking and ex-smoking severe asthma molecular phenotypes.The U-BIOPRED cohort of severe asthma patients, containing current-smokers (CSA), ex-smokers (ESA), nonsmokers and healthy nonsmokers was examined. Blood and sputum cell counts, fractional exhaled nitric oxide and spirometry were obtained. Exploratory proteomic analysis of sputum supernatants and transcriptomic analysis of bronchial brushings, biopsies and sputum cells was performed.Colony-stimulating factor (CSF)2 protein levels were increased in CSA sputum supernatants, with azurocidin 1, neutrophil elastase and CXCL8 upregulated in ESA. Phagocytosis and innate immune pathways were associated with neutrophilic inflammation in ESA. Gene set variation analysis of bronchial epithelial cell transcriptome from CSA showed enrichment of xenobiotic metabolism, oxidative stress and endoplasmic reticulum stress compared to other groups. CXCL5 and matrix metallopeptidase 12 genes were upregulated in ESA and the epithelial protective genes, mucin 2 and cystatin SN, were downregulated.Despite little difference in clinical characteristics, CSA were distinguishable from ESA subjects at the sputum proteomic level, with CSA patients having increased CSF2 expression and ESA patients showing sustained loss of epithelial barrier processes.

AMPK alleviates endoplasmic reticulum stress by inducing the ER-chaperone ORP150 via FOXO1 to protect human bronchial cells from apoptosis

Chronic obstructive pulmonary disease (COPD), is characterized by inflammation of airways accompanied by a progressive destruction of lung parenchyma. This process is initiated in most cases by cigarette smoking. In this study we investigated the role of AMP activated protein kinase (AMPK) in cigarette smoke extract (CSE)-induced airway epithelial cell apoptosis as a consequence of endoplasmic reticulum stress (ER stress). Exposure of human bronchial epithelial cells (HBEpC) to CSE resulted in apoptosis as detected using Annexin V-PI flow cytometry. However, co-treatment with N1-(β-d-ribofuranosyl)-5-aminoimidazole-4-carboxamide (AICAR), a pharmacological activator of AMPK, significantly increased cell protection against ER stress-induced apoptosis by upregulating the 150 kDa oxygen-regulated protein (ORP150), which functions as an ER-associated chaperone, with concomitant elevation of FOXO1, a critical transcription factor regulating ORP150 expression. Lentiviral silencing of AMPK or FOXO1 using short hairpin (sh) RNA resulted in a significant decrease of ORP150 and an elevation of CCAAT/enhancer-binding protein-homologous protein (CHOP) resulting in ER stress and apoptosis of HBEpC. Together, our results strongly suggest that AMPK can activate ORP150 through FOXO1 pathway and confer protection against ER stress-induced apoptosis of airway epithelial cells following exposure to CSE. Thus, AMPK may serve as a likely therapeutic target for clinical and sub-clinical interventions in COPD.

The mitochondrial and endoplasmic reticulum pathways involved in the apoptosis of bursa of Fabricius cells in broilers exposed to dietary aflatoxin B1

Aflatoxin B₁ (AFB₁), a toxic metabolite produced by some fungi, exerts well-known hepatocarcinogenic and immunosuppressive effects, the latter can increase the apoptotic immune cells in vitro. However, it is largely unknown that which signaling pathways contribute to excessive apoptosis of immune cells which induced by AFB₁. In this study, we investigated the roles of the mitochondria, endoplasmic reticulum (ER) and death receptor activated apoptotic pathways in the bursal of Fabricius (BF) cells in the broilers exposed to AFB₁ diet. We found that (1) AFB₁ diet induced morphological changes in the BF. (2) FCM and TUNEL methods showed that excessive apoptosis could be resulted from AFB₁ intake. (3) AFB₁-induced apoptosis of bursal cells involved mitochondrial pathway (increase of Bax, Bak, cytC, caspase-9, Apaf-1, caspase-3 and decrease of Bcl-2 and Bcl-xL) and ER pathway (increase of Grp78/Bip, Grp94 and CaM). (4) Oxidative stress was confirmed in the BF of chicken fed on AFB₁ diet. Overall, this work is the first to demonstrate that the activation of mitochondria and ER apoptosis pathways can lead to excessive apoptosis in BF cells, and oxidative stress is a crucial driver during AFB₁ exposure.

Induction of ER and mitochondrial stress by the alkylphosphocholine erufosine in oral squamous cell carcinoma cells

Endoplasmic reticulum (ER) plays an essential role in cell function and survival. Accumulation of unfolded or misfolded proteins in the lumen of the ER activates the unfolded protein response (UPR), resulting in ER stress and subsequent apoptosis. The alkylphosphocholine erufosine is a known Akt-mTOR inhibitor in oral squamous cell carcinoma (OSCC). In the present study, we evaluate erufosine’s role to induce ER and mitochondrial stress leading to autophagy, apoptosis, and ROS induction. The cellular toxicity of erufosine was determined in two OSCC cell lines and gene expression and enrichment analyses were performed. A positive enrichment of ER stress upon erufosine exposure was observed, which was verified at protein levels for the ER stress sensors and their downstream mediators. Knockdown and pharmacological inhibition of the ER stress sensors PERK and XBP1 revealed their involvement into erufosine’s cellular effects, including proliferation, apoptosis, and autophagy induction. Autophagy was confirmed by increased acidic vacuoles and LC3-B levels. Upon erufosine exposure, calcium influx into the cytoplasm of the two OSCC cell lines was seen. Apoptosis was confirmed by nuclear staining, Annexin-V, and immunoblotting of caspases. The induction of mitochondrial stress upon erufosine exposure was predicted by gene set enrichment analysis (GSEA) and shown by erufosine’s effect on mitochondrial membrane potential, ATP, and ROS production in OSCC cells. These data show that ER and mitochondrial targeting by erufosine represents a new facet of its mechanism of action as well as a promising new framework in the treatment of head and neck cancers.

Schlafen2 mutation unravels a role for chronic ER stress in the loss of T cell quiescence

Immunologically naïve lymphocytes are kept in a quiescent state until antigen engagement. These quiescent immune cells are characterized by small cell size, lack of spontaneous proliferation and low metabolic rate. Lymphocyte quiescence is actively enforced condition which ensures the preservation of proper differentiation and proliferation capabilities of naïve and memory lymphocytes. Previously we described a chemically induced mutation in Schlafen2 (Slfn2), termed elektra, which breaks quiescence and compromises immunity. However, the mechanism by which Slfn2 maintains quiescence remains unknown. Here we demonstrate that elektra T cells display chronic ER stress under steady state conditions. Modulation of ER stress response by depletion of either UPR mediators XBP1 or CHOP, improved viability and partially corrected the developmental abnormalities and proliferation capabilities of elektra T cells. Altogether, our results demonstrate a functional connection between Slfn2 induced quiescence in T cells and ER homeostasis, clarifying a novel mechanism by which immune cell quiescence is maintained.

Protein Folding in the Presence of Water-Soluble Cyclic Diselenides with Novel Oxidoreductase and Isomerase Activities

The protein disulfide isomerase (PDI) family, found in the endoplasmic reticulum (ER) of the eukaryotic cell, catalyzes the formation and cleavage of disulfide bonds and thereby helps in protein folding. A decrease in PDI activity under ER stress conditions leads to protein misfolding, which is responsible for the progression of various human diseases, such as Alzheimer's, Parkinson's, diabetes mellitus, and atherosclerosis. Here we report that water-soluble cyclic diselenides mimic the multifunctional activity of the PDI family by facilitating oxidative folding, disulfide formation/reduction, and repair of the scrambled disulfide bonds in misfolded proteins.

Inhibition of endoplasmic reticulum stress alleviates cigarette smoke-induced airway inflammation and emphysema

Chronic bronchitis and emphysema are pathologic features of chronic obstructive pulmonary disease (COPD). Cigarette smoke (CS)-induced endoplasmic reticulum (ER) stress has been implicated in the COPD development, but the molecular mechanism by which it contributes to COPD etiology and the specific role it plays in COPD pathogenesis remain poorly understood. Here, we aimed to determine the role of ER stress in the pathogenesis of CS-induced airway inflammation and emphysema. Exposure to CS significantly increased the expression of ER stress markers in Beas-2B cells and in mouse lungs, possibly through the production of oxidative stress. Further, inhibition of ER stress by 4-phenylbutyric acid (4-PBA) reduced CS extract-induced inflammation in Beas-2B cells through the modulation of NF-κB signaling. 4-PBA also protected against CS-induced airway inflammation and the development of emphysema in mice, which was associated with a reduction in NF-κB activation and alveolar cell apoptosis in the lungs. Taken together, our results suggest that ER stress is crucial for CS-induced inflammation and emphysema, and that targeting ER stress may represent a novel approach to the treatment of COPD.

Poxviruses Utilize Multiple Strategies to Inhibit Apoptosis

Cells have multiple means to induce apoptosis in response to viral infection. Poxviruses must prevent activation of cellular apoptosis to ensure successful replication. These viruses devote a substantial portion of their genome to immune evasion. Many of these immune evasion products expressed during infection antagonize cellular apoptotic pathways. Poxvirus products target multiple points in both the extrinsic and intrinsic apoptotic pathways, thereby mitigating apoptosis during infection. Interestingly, recent evidence indicates that poxviruses also hijack cellular means of eliminating apoptotic bodies as a means to spread cell to cell through a process called apoptotic mimicry. Poxviruses are the causative agent of many human and veterinary diseases. Further, there is substantial interest in developing these viruses as vectors for a variety of uses including vaccine delivery and as oncolytic viruses to treat certain human cancers. Therefore, an understanding of the molecular mechanisms through which poxviruses regulate the cellular apoptotic pathways remains a top research priority. In this review, we consider anti-apoptotic strategies of poxviruses focusing on three relevant poxvirus genera: Orthopoxvirus, Molluscipoxvirus, and Leporipoxvirus. All three genera express multiple products to inhibit both extrinsic and intrinsic apoptotic pathways with many of these products required for virulence.

Hydrogen sulfide ameliorates cognitive dysfunction in streptozotocin-induced diabetic rats: involving suppression in hippocampal endoplasmic reticulum stress

Diabetes induces impairment in cognitive function. There is substantial evidence that hippocampal endoplasmic reticulum (ER) stress is involved in diabetic cognitive impairment. Hydrogen sulfide (H₂S) attenuates the learning and memory decline in experimental Alzheimer's disease and inhibits the hippocampal ER stress in homocysteine-exposed rats. Therefore, this aim of the present work was to investigate whether H₂S ameliorates the diabetic cognitive dysfunction involving inhibition of hippocampal ER stress. In the present work, we found that stretozotocin (STZ, 40 mg/kg)-induced diabetic rats exhibited impairment in cognitive function, as judged by the novel objective recognition task (NOR) test, the Y-maze test and the Morris water maze (MWM) test. Notably, treatment of diabetic rats with sodium hydrosulfide (NaHS, a donor of H₂S, 30 or 100 μmol/kg/d, for 30 d) significantly reversed diabetes-induced impairment in cognitive function. We also found that STZ (40 mg/kg)-induced diabetic rats exhibited hippocampal ER stress, as evidenced by upregulations of glucose regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), and cleaved caspase-12 in the hippocampus. However, treatment with NaHS (30 or 100 μmol/kg/d, for 30 d) markedly suppressed the increases in GRP78, CHOP, and cleaved caspase-12 expressions in the hippocampus of diabetic rats. In addition, we noted that NaHS (30 or 100 μmol/kg/d, for 30 d) significantly enhanced the generation of hippocampal endogenous H₂S in STZ-induced diabetic rats. These results suggest that H₂S exhibits therapeutic potential for diabetes-associated cognitive dysfunction, which is most likely related to its protective effects against hippocampal ER stress.

Reactive oxygen species-mediated unfolded protein response pathways in preimplantation embryos

Excessive production of reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress-mediated responses are critical to embryonic development in the challenging in vitro environment. ROS production increases during early embryonic development with the increase in protein requirements for cell survival and growth. The ER is a multifunctional cellular organelle responsible for protein folding, modification, and cellular homeostasis. ER stress is activated by a variety of factors including ROS. Such stress leads to activation of the adaptive unfolded protein response (UPR), which restores homeostasis. However, chronic stress can exceed the toleration level of the ER, resulting in cellular apoptosis. In this review, we briefly describe the generation and impact of ROS in preimplantation embryo development, the ROS-mediated activation mechanism of the UPR via the ER, and the subsequent activation of signaling pathways following ER stress in preimplantation embryos.

Nilotinib induces ER stress and cell death in H9c2 cells

Tyrosine kinases inhibitors (TKi) represent a relatively novel class of anticancer drugs that target cellular pathways overexpressed in certain types of malignancies, such as chronic myeloid leukaemia (CML). Nilotinib, ponatinib and imatinib exhibit cardiotoxic and vascular effects. In this study, we focused on possible cardiotoxicity of nilotinib using H9c2 cells as a suitable cell model. We studied role of endoplasmic reticulum (ER) stress and apoptosis in nilotinib toxicity using a complex approach. Nilotinib impaired mitochondrial function and induced formation of ROS under clinically relevant concentrations. In addition, ability of nilotinib to induce ER stress has been shown. These events result in apoptotic cell death. All these mechanisms contribute to cytotoxic effect of the drug. In addition, involvement of ER stress in nilotinib toxicity may be important in co-treatment with pharmaceuticals affecting ER and ER stress, e.g. beta-blockers or sartans, and should be further investigated.

Gu-Ben-Fang-Xiao decoction attenuates sustained airway inflammation by suppressing ER stress response in a murine asthma remission model of respiratory syncytial virus infection

ETHNOPHARMACOLOGICAL RELEVANCE

In recent years, asthma has increased dramatically in prevalence with a considerable economic burden all over the world. Long-term remission should be regarded as the promising and meaningful therapeutic goal in asthma management. However, the precise definition criteria and rational therapies for asthma remission have not been well-established. In academia, there is a consensus that even in those who develop asymptomatic remission of asthma, persistent airway inflammation is ubiquitous. Gubenfangxiao decoction (GBFXD) has been widely used in treating asthma remission stage for decades in the Jiangsu Province Hospital of Chinese Medicine, China. We previously demonstrated that GBFXD could downregulate the asthma susceptibility gene ORMDL3, a trigger of Endoplasmic reticulum (ER) stress and unfolded protein response (UPR).

AIM THIS STUDY

To investigate the involvement of ER stress and UPR in the anti-inflammatory effects of GBFXD in Respiratory Syncytial Virus (RSV)-OVA-induced asthma remission mice.

MATERIALS AND METHODS

Mice were orally administered GBFXD at three doses for 30 days after an RSV-OVA challenge. The levels of inflammation mediators in serum were measured using a Luminex assay and the amount of IFN-γ in lung homogenates was detected using ELISA. The splenic CD4+ and CD8+ T lymphocytes were counted using flow cytometric analysis. The mRNA and protein levels of asthma susceptibility gene ORMDL3, ER stress markers (BIP, CHOP), and three canonical UPR branches (PERK-eIF2a-ATF4, IRE1α-XBP1/IRE1α-JNK-AP1 and ATF6-SERCA2b signal pathways) were detected using real-time RT-PCR and western blot.

RESULTS

Histopathological analysis showed that the model group mice still exhibited a sustained airway inflammation even after suspending the OVA-challenge and RSV infections for 30 days. H&E staining results indicated that GBFXD could attenuate sustained airway inflammation. Decreased serum CXCL1 level and increased IFN-γ level in lung homogenate were observed after GBFXD treatment. Reductions in the number of splenic CD4+/CD8+ T lymphocytes were found after DEX treatment. We further confirmed the previous finding that GBFXD could downregulate the expression of ORMDL3. As a result of suppressed UPR, decreased ER stress markers and inhibited UPR branches (PERK and IRE1α signal pathway) were also observed through the significant reduction of signature mRNA and protein expressions after GBFXD treatment.

CONCLUSION

GBFXD can significantly attenuate RSV-OVA-induced persistent airway inflammation in murine asthma remission model. These effects may be mediated, at least partially, by inhibiting the activation of ER stress responses.

Astragalus polysaccharide modulates ER stress response in an OVA-LPS induced murine model of severe asthma

Endoplasmic reticulum (ER) stress has been recently revealed to play a pivotal role in the pathogenesis of severe asthma. Astragalus polysaccharide (APS), a major bioactive component from Astragalus membranaceus, exerts immunomodulatory and anti-inflammatory effects and has been shown to suppress ER stress in chronic diseases such as type-2 diabetes. However, the pharmaceutical application of APS in the treatment of severe asthma is unknown. The results obtained here indicate that APS significantly attenuates eosinophils and neutrophil-dominant airway inflammation by reducing the mRNA levels of Cxcl5, Il8, and chemokine (C-C motif) ligand 20 (Ccl20) and the protein levels of IL13RA and IL17RA. APS also inhibits the activation of unfolded protein response by decreasing the levels of ER stress markers such as C/EBP homologous protein (CHOP), which was associated with a reduction of PERK phosphorylation. Moreover, APS substantially blocks the nuclear translocation of ATF6 and NF-κB p65. Interestingly, we observed that APS markedly suppresses mucus hypersecretion by decreasing the levels of mucin (MUC) 5AC and MUC5B, which might be due to inhibition of goblet cells differentiation by suppressing the expression of IRE1β-correlated genes. In summary, APS can have potential pharmaceutical application in treatment of severe asthma.

ER Stress-Mediated Signaling: Action Potential and Ca(2+) as Key Players

The proper functioning of the endoplasmic reticulum (ER) is crucial for multiple cellular activities and survival. Disturbances in the normal ER functions lead to the accumulation and aggregation of unfolded proteins, which initiates an adaptive response, the unfolded protein response (UPR), in order to regain normal ER functions. Failure to activate the adaptive response initiates the process of programmed cell death or apoptosis. Apoptosis plays an important role in cell elimination, which is essential for embryogenesis, development, and tissue homeostasis. Impaired apoptosis can lead to the development of various pathological conditions, such as neurodegenerative and autoimmune diseases, cancer, or acquired immune deficiency syndrome (AIDS). Calcium (Ca(2+)) is one of the key regulators of cell survival and it can induce ER stress-mediated apoptosis in response to various conditions. Ca(2+) regulates cell death both at the early and late stages of apoptosis. Severe Ca(2+) dysregulation can promote cell death through apoptosis. Action potential, an electrical signal transmitted along the neurons and muscle fibers, is important for conveying information to, from, and within the brain. Upon the initiation of the action potential, increased levels of cytosolic Ca(2+) (depolarization) lead to the activation of the ER stress response involved in the initiation of apoptosis. In this review, we discuss the involvement of Ca(2+) and action potential in ER stress-mediated apoptosis.

Non-thermal gas plasma-induced endoplasmic reticulum stress mediates apoptosis in human colon cancer cells

Colorectal cancer is a common type of tumor among both men and women worldwide. Conventional remedies such as chemotherapies pose the risk of side‑effects, and in many cases cancer cells develop chemoresistance to these treatments. Non‑thermal gas plasma (NTGP) was recently identified as a potential tool for cancer treatment. In this study, we investigated the potential use of NTGP to control SNUC5 human colon carcinoma cells. We hypothesized that NTGP would generate reactive oxygen species (ROS) in these cells, resulting in induction of endoplasmic reticulum (ER) stress. ROS generation, expression of ER stress‑related proteins and mitochondrial calcium levels were analyzed. Our results confirmed that plasma‑generated ROS induce apoptosis in SNUC5 cells. Furthermore, we found that plasma exposure resulted in mitochondrial calcium accumulation and expression of unfolded protein response (UPR) proteins such as glucose‑related protein 78 (GRP78), protein kinase R (PKR)‑like ER kinase (PERK), and inositol‑requiring enzyme 1 (IRE1). Elevated expression of spliced X‑box binding protein 1 (XBP1) and CCAAT/enhancer‑binding protein homologous protein (CHOP) further confirmed that ROS generated by NTGP induces apoptosis through the ER stress signaling pathway.

Penehyclidine Hydrochloride Pretreatment Ameliorates Rhabdomyolysis-Induced AKI by Activating the Nrf2/HO-1 Pathway and Alleviating [corrected] Endoplasmic Reticulum Stress in Rats. The

Acute kidney injury (AKI) is one of the most severe complications of rhabdomyolysis (RM). The underlying mechanisms and potential preventions need to be investigated. Penehyclidine hydrochloride (PHC) was reported to ameliorate renal ischemia-reperfusion injury, but the effect of PHC on RM-reduced AKI is unknown. In this study, we established a rat model of RM-induced AKI using an intramuscular glycerol injection in the hind limbs. Rats were pretreated with PHC before the glycerol injection, and the heme oxygenase-1 (HO-1) inhibitor ZnPP was introduced to evaluate the effect of HO-1 on RM-induced AKI. PHC pretreatment ameliorated the pathological renal injury and renal dysfunction, and decreased the renal apoptosis rate in RM-induced AKI. PHC significantly up-regulated HO-1 expression, increased HO-1 enzymatic activity and decreased the accumulation of myoglobin in renal tissues. This effect was partly inhibited by ZnPP. PHC pretreatment also effectively up-regulated nuclear factor erythroid 2-related factor 2 (Nrf2) and down-regulated glucose regulated protein 78 (GRP78) and caspase-12 at both the gene and protein levels. These results suggest that the protective effects of PHC pretreatment on RM-induced AKI occur at least in part through activating the Nrf2/HO-1 pathway and alleviating endoplasmic reticulum stress (ERS) in rat renal tissues.

Rhabdomyolysis induced AKI via the regulation of endoplasmic reticulum stress and oxidative stress in PTECs

Mechanism for the role of ER stress and oxidative stress activation in rhabdomyolysis-associated AKI.

OASIS modulates hypoxia pathway activity to regulate bone angiogenesis

OASIS/CREB3L1, an endoplasmic reticulum (ER)-resident transcription factor, plays important roles in osteoblast differentiation. In this study, we identified new crosstalk between OASIS and the hypoxia signaling pathway, which regulates vascularization during bone development. RT-PCR and real-time PCR analyses revealed significant decreases in the expression levels of hypoxia-inducible factor-1α (HIF-1α) target genes such as vascular endothelial growth factor A (VEGFA) in OASIS-deficient (Oasis^−/−) mouse embryonic fibroblasts. In coimmunoprecipitation experiments, the N-terminal fragment of OASIS (OASIS-N; activated form of OASIS) bound to HIF-1α through the bZIP domain. Luciferase assays showed that OASIS-N promoted the transcription activities of a reporter gene via a hypoxia-response element (HRE). Furthermore, the expression levels of an angiogenic factor Vegfa was decreased in Oasis^−/− osteoblasts. Immunostaining and metatarsal angiogenesis assay showed retarded vascularization in bone tissue of Oasis^−/− mice. These results suggest that OASIS affects the expression of HIF-1α target genes through the protein interaction with HIF-1α, and that OASIS-HIF-1α complexes may play essential roles in angiogenesis during bone development.

Phosphoinositide 3-kinase-δ regulates fungus-induced allergic lung inflammation through endoplasmic reticulum stress

Background

Sensitisation with Aspergillus fumigatus (Af) is known to be associated with severe allergic lung inflammation, but the mechanism remains to be clarified. Phosphoinositide 3-kinase (PI3K)-δ and endoplasmic reticulum (ER) stress are suggested to be involved in steroid-resistant lung inflammation. We aimed to elucidate the role of PI3K-δ and its relationship with ER stress in fungus-induced allergic lung inflammation.

Methods

Using Af-exposed in vivo and in vitro experimental systems, we examined whether PI3K-δ regulates ER stress, thereby contributing to steroid resistance in fungus-induced allergic lung inflammation. Moreover, we checked expression of an ER stress marker in lung tissues isolated from patients with allergic bronchopulmonary aspergillosis.

Results

Af-exposed mice showed that ER stress markers, unfolded protein response (UPR)-related proteins, phosphorylated Akt, generation of mitochondrial reactive oxygen species (mtROS), eosinophilic allergic inflammation, and airway hyperresponsiveness (AHR) were increased in the lung. Similarly, glucose-regulated protein 78 was increased in lung tissues of patients with ABPA. A PI3K-δ inhibitor reduced Af-induced increases in ER stress markers, UPR-related proteins, allergic inflammation and AHR in mice. However, dexamethasone failed to reduce Af-induced allergic inflammation, AHR and elevation of ER stress. Administration of an ER stress inhibitor or a mtROS scavenger improved Af-induced allergic inflammation. The PI3K-δ inhibitor reduced Af-induced mtROS generation and the mtROS scavenger ameliorated ER stress. In primary cultured tracheal epithelial cells, Af-induced ER stress was inhibited by blockade of PI3K-δ.

Conclusions

These findings suggest that PI3K-δ regulates Af-induced steroid-resistant eosinophilic allergic lung inflammation through ER stress.

Polycation-mediated integrated cell death processes

One of the major challenges in the field of nucleic acid delivery is the design of delivery vehicles with attributes that render them safe as well as efficient in transfection. To this end, polycationic vectors have been intensely investigated with native polyethylenimines (PEIs) being the gold standard. PEIs are highly efficient transfectants, but depending on their architecture and size they induce cytotoxicity through different modes of cell death pathways. Here, we briefly review dynamic and integrated cell death processes and pathways, and discuss considerations in cell death assay design and their interpretation in relation to PEIs and PEI-based engineered vectors, which are also translatable for the design and studying the safety of other transfectants.

Cyclin D1 sensitizes myeloma cells to endoplasmic reticulum stress-mediated apoptosis by activating the unfolded protein response pathway

Background

Cyclin D1 and its kinase partners control cell cycle progression. Cyclin D1 is frequently deregulated in various cancers, including malignant hemopathies, and tumor cells display uncontrolled cell proliferation. Cyclin D1 is not expressed in the B-cell lineage but is found in multiple myeloma (MM) cells in almost 50% of patients with this condition. Paradoxically, cyclin D1 expression is associated with a good prognosis and longer overall survival in MM patients.

Methods

We used two independent MM cell lines (RPMI 8226 and LP1) to generate several clones stably expressing either the green fluorescent protein (GFP) or a GFP-cyclin D1 fusion protein, and we analyzed the properties acquired following cyclin D1 expression.

Results

Whole-genome expression analysis in the cell clones indicated that cyclin D1 profoundly modified several cellular functions, including the regulation of apoptotic cell death. We studied the apoptotic response of GFP- and GFP-cyclin D1-expressing clones to bortezomib-treatment. We found that the apoptotic response occurred faster and was of a greater amplitude in cyclin D1-expressing cells. Cyclin D1 expression enhanced the caspase-dependent apoptosis mediated by the intrinsic mitochondrial pathway. More importantly, cyclin D1 also activated the unfolded protein response (UPR) and induced endoplasmic reticulum (ER) stress-mediated apoptosis.

Conclusion

The ER is well known to be a crucial regulator of plasma cell death and it plays the same role in their malignant counterparts, myeloma cells. This role involves activation of the UPR controlled at least in part by cyclin D1.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1240-y) contains supplementary material, which is available to authorized users.

Natural history of β-cell adaptation and failure in type 2 diabetes

Type 2 diabetes mellitus (T2D) is a complex disease characterized by β-cell failure in the setting of insulin resistance. The current evidence suggests that genetic predisposition, and environmental factors can impair the capacity of the β-cells to respond to insulin resistance and ultimately lead to their failure. However, genetic studies have demonstrated that known variants account for less than 10% of the overall estimated T2D risk, suggesting that additional unidentified factors contribute to susceptibility of this disease. In this review, we will discuss the different stages that contribute to the development of β-cell failure in T2D. We divide the natural history of this process in three major stages: susceptibility, β-cell adaptation and β-cell failure, and provide an overview of the molecular mechanisms involved. Further research into mechanisms will reveal key modulators of β-cell failure and thus identify possible novel therapeutic targets and potential interventions to protect against β-cell failure.

At the right distance: ER-mitochondria juxtaposition in cell life and death

The interface between mitochondria and the endoplasmic reticulum is emerging as a crucial hub for calcium signalling, apoptosis, autophagy and lipid biosynthesis, with far reaching implications in cell life and death and in the regulation of mitochondrial and endoplasmic reticulum function. Here we review our current knowledge on the structural and functional aspects of this interorganellar juxtaposition. This article is part of a Special Issue entitled: Calcium Signaling In Health and Disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.

Protein Disulfide Isomerase Superfamily in Disease and the Regulation of Apoptosis

Cellular homeostasis requires the balance of a multitude of signaling cascades that are contingent upon the essential proteins being properly synthesized, folded and delivered to appropriate subcellular locations. In eukaryotic cells the endoplasmic reticulum (ER) is a specialized organelle that is the central site of synthesis and folding of secretory, membrane and a number of organelletargeted proteins. The integrity of protein folding is enabled by the presence of ATP, Ca++, molecular chaperones, as well as an oxidizing redox environment. The imbalance between the load and capacity of protein folding results in a cellular condition known as ER stress. Failure of these pathways to restore ER homeostasis results in the activation of apoptotic pathways. Protein disulfide isomerases (PDI) compose a superfamily of oxidoreductases that have diverse sequences and are localized in the ER, nucleus, cytosol, mitochondria and cell membrane. The PDI superfamily has multiple functions including, acting as molecular chaperones, protein-binding partners, and hormone reservoirs. Recently, PDI family members have been implicated in the regulation of apoptotic signaling events. The complexities underlying the molecular mechanisms that define the switch from pro-survival to pro-death response are evidenced by recent studies that reveal the roles of specific chaperone proteins as integration points in signaling pathways that determine cell fate. The following review discusses the dual role of PDI in cell death and survival during ER stress.

New directions in ER stress-induced cell death

Endoplasmic reticulum (ER) stress has been implicated in the pathophysiology of many diseases including heart disease, cancer and neurodegenerative diseases such as Alzheimer's and Huntington's. Prolonged or excessive ER stress results in the initiation of signaling pathways resulting in cell death. Over the past decade much research investigating the onset and progression of ER stress-induced cell death has been carried out. Owing to this we now have a better understanding of the signaling pathways leading to ER stress-mediated cell death and have begun to appreciate the importance of ER localized stress sensors, IRE1α, ATF6 and PERK in this process. In this article we provide an overview of the current thinking and concepts concerning the various stages of ER stress-induced cell death, focusing on the role of ER localized proteins in sensing and triggering ER stress-induced death signals with particular emphasis on the contribution of calcium signaling and Bcl-2 family members to the execution phase of this process. We also highlight new and emerging directions in ER stress-induced cell death research particularly the role of microRNAs, ER-mitochondria cross talk and the prospect of mitochondria-independent death signals in ER stress-induced cell death.

Endoplasmic reticulum stress influences bronchial asthma pathogenesis by modulating nuclear factor κB activation

BACKGROUND

Despite many studies on endoplasmic reticulum (ER) stress in patients with various inflammatory diseases, there is scarce information on ER stress in patients with bronchial asthma.

OBJECTIVE

In this study we aimed to elucidate the role of ER stress in the pathogenesis of bronchial asthma.

METHODS

Using mice sensitized with ovalbumin (OVA) and LPS and challenged with OVA (OVA(LPS)-OVA mice), as well as mice sensitized and challenged with OVA (OVA-OVA mice), we investigated whether ER stress is involved in the pathogenesis of bronchial asthma. Moreover, we also determined the levels of ER stress markers in blood and bronchoalveolar lavage fluid from asthmatic patients.

RESULTS

The OVA(LPS)-OVA mice showed that the expression of ER stress markers and the protein levels of unfolded protein response-related markers in lung tissue were significantly increased after OVA challenge. Moreover, we found that ER stress markers in PBMCs and bronchoalveolar lavage fluid from human asthmatic patients were dramatically increased compared with those from healthy control subjects. In OVA(LPS)-OVA mice 4-phenylbutyric acid (4-PBA), a chemical chaperone, significantly reduced the increases in ER stress, nuclear translocation of nuclear factor κB, inflammatory cytokine levels, dendritic cell infiltration, Toll-like receptor 4 expression, airway inflammation, and bronchial hyperresponsiveness, whereas it further enhanced the increase in IL-10 levels. Additionally, the established asthmatic features of OVA-OVA mice were substantially attenuated by 4-PBA administered after completion of OVA challenge.

CONCLUSION

These results indicate that ER stress might be implicated in the pathogenesis of bronchial asthma at least in part through modulation of nuclear factor κB activation.

Functional and morphological impact of ER stress on mitochondria

Over the past years, knowledge and evidence about the existence of crosstalks between cellular organelles and their potential effects on survival or cell death have been constantly growing. More recently, evidence accumulated showing an intimate relationship between endoplasmic reticulum (ER) and mitochondria. These close contacts not only establish extensive physical links allowing exchange of lipids and calcium but they can also coordinate pathways involved in cell life and death. It is now obvious that ER dysfunction/stress and unfolded protein response (UPR) as well as mitochondria play major roles in apoptosis. However, while the effects of major ER stress on cell death have been largely studied and reviewed, it becomes more and more evident that cells might regularly deal with sublethal ER stress, a condition that does not necessarily lead to cell death but might affect the function/activity of other organelles such as mitochondria. In this review, we will particularly focus on these new, interesting and intriguing metabolic and morphological events that occur during the early adaptative phase of the ER stress, before the onset of cell death, and that remain largely unknown. Relevance and implication of these mitochondrial changes in response to ER stress conditions for human diseases such as type II diabetes and Alzheimer's disease will also be considered.