Gadd153 sensitizes cells to endoplasmic reticulum stress by down-regulating Bcl2 and perturbing the cellular redox state

Mitonuclear Communication in Stem Cell Function

Mitochondria perform multiple functions within the cell, including the production of ATP and a great deal of metabolic intermediates, while also contributing to the cellular stress response. The majority of mitochondrial proteins are encoded by nuclear genomes, highlighting the importance of mitonuclear communication for sustaining mitochondrial homeostasis and functional. As a crucial part of the intracellular signalling network, mitochondria can impact stem cell fate determinations. Considering the essential function of stem cells in tissue maintenance, regeneration and aging, it is important to understand how mitochondria influence stem cell fate. This review explores the significant roles of mitonuclear communication and mitochondrial proteostasis, highlighting their influence on stem cells. We also examine how mitonuclear interactions contribute to cellular homeostasis, stem cell therapies, and the potential for extending lifespan.

Quercetin alleviates cerebral ischemia and reperfusion injury in hyperglycemic animals by reducing endoplasmic reticulum stress through activating SIRT1

Hyperglycemia aggravates cerebral ischemic reperfusion injury (CIRI). Neuroprotective drugs that are effective in reducing CIRI in animals with normoglycemic condition are ineffective in ameliorating CIRI under hyperglycemic condition. This study investigated whether quercetin alleviates hyperglycemic CIRI by inhibiting endoplasmic reticulum stress (ERS) through modulating the SIRT1 signaling pathway. A middle cerebral artery occlusion/reperfusion (MCAO/R) model was induced in STZ-injected hyperglycemic rats. High glucose and oxygen glucose deprivation/reoxygenation (OGD/R) models were established in HT22 cells. The results demonstrated that hyperglycemia exacerbated CIRI, and quercetin pretreatment decreased the neurological deficit score and cerebral infarct volume, and alleviated neuron damage in the cortex of the penumbra in hyperglycemic MCAO/R rats, indicating that quercetin could be a candidate for treating hyperglycemic CIRI. Moreover, quercetin pretreatment reduced apoptosis, inhibited the expression of the ERS marker proteins GRP78 and ATF6, and mitigated the expression of the ERS-mediated proapoptotic protein CHOP in hyperglycemic MCAO/R rats, suggesting that quercetin alleviated hyperglycemic CIRI by inhibiting ERS and ERS-mediated apoptosis. Furthermore, quercetin upregulated Sirt1 expression in HG+OGD/R treated HT22 cells and inhibited PERK, p-eIF2α, ATF4, and CHOP expression. In contrast, the SIRT1 selective inhibitor EX-527 blocked the effect of quercetin on protein expression in the SIRT1/PERK pathway and aggravated HT22 cell injury. These findings indicate that quercetin inhibits ERS-mediated apoptosis through modulating the SIRT1 and PERK pathway. In conclusion, quercetin alleviates hyperglycemic CIRI by inhibiting ERS-mediated apoptosis through activating SIRT1 that consequently suppressed ERS signaling.

Role of C/EBP Homologous Protein (CHOP) and Nupr1 Interaction in Endoplasmic Reticulum Stress-Induced Apoptosis of Lens Epithelial Cells

Our study mainly analyzed the mechanism of C/EBP homologous protein (CHOP) and its interacting protein Nupr1 on endoplasmic reticulum stress (ERS) induced lens epithelial cells (LEC) apoptosis. Cell proliferation was detected by CCK-8. Apoptosis was detected by flow cytometry and TUNEL. Nupr1 expression was detected by RT-qPCR. The expressions of CHOP, Nupr1, apoptosis-related protein, and ERS-related protein were detected by Western blot. DCFH-DA probe was used to detect cell ROS. The SOD, GSH-PX, and MDA contents were detected by the kit. Co-IP was used to detect the interaction between CHOP and Nupr1. The morphology of the lens was detected by HE staining. The result shows that Tunicamycin (TU) can induce endoplasmic reticulum stress and apoptosis in LEC in a concentration-dependent manner. TU induction leads to the occurrence of CHOP nuclear translocation. Overexpression of CHOP can further enhance the inhibitory effect of TU on LEC proliferation and the promotion of apoptosis, while knockdown of CHOP has the opposite effect. CHOP and Nupr1 are interacting proteins, and knockdown of Nupr1 or addition of Nupr1 inhibitor ZZW-115 can reverse the effects of TU and overexpression of CHOP, respectively. It has been observed in animal experiments that treatment with oe-CHOP can further aggravate the pathological lesions of the rat lens, while ZZW-115 can reverse the effect of oe-CHOP to a certain extent and improve the lesions of the rat lens. Overall, CHOP interacts with Nupr1 to regulate apoptosis caused by ERS and mediate cataract progression in rats, and this study provides a new potential therapeutic target for the treatment of cataract.

Lycopene mitigates paclitaxel-induced cognitive impairment in mice; Insights into Nrf2/HO-1, NF-κB/NLRP3, and GRP-78/ATF-6 axes

Chemotherapy-induced cognitive impairment, referred to as "chemobrain", is widely acknowledged as a significant adverse effect of cancer therapy. Paclitaxel, a chemotherapeutic drug, has been reported to cause cognitive impairment clinically and in animal models. However, the precise mechanisms are not fully understood. The current study explored the potential neuroprotective effect of lycopene in paclitaxel-induced cognitive impairment in mice and its potential underlying mechanisms. Mice were randomly allocated into six groups: control, paclitaxel-treated (10 mg/kg), lycopene-treated (5, 10, and 20 mg/kg) + paclitaxel, and lycopene alone-treated (20 mg/kg) groups. The effect of lycopene treatment on behavioral function and histological examination was assessed. Lycopene (20 mg/kg) was selected for additional investigation into the underlying mechanisms. Lycopene treatment counteracted paclitaxel-induced oxidative stress by reducing lipid peroxidation and enhancing catalase levels. Additionally, lycopene-treated mice demonstrated a significant elevation in nuclear factor erythroid 2-related factor 2 with no significant effect on hemeoxygenase-1. Moreover, paclitaxel administration elevated endoplasmic reticulum stress markers; glucose-regulated protein78, activating Transcription Factor 6, C/EBP homologous protein, and apoptosis marker annexin V which were significantly reduced by lycopene treatment. Furthermore, lycopene mitigated paclitaxel-induced neuroinflammation through the reduction of the levels of the NLR Family Pyrin Domain Containing 3 (NLRP3) inflammasome axis markers; nuclear factor-κB, NLRP3, caspase-1, interleukin-1β, and interleukin-18. Our study findings may provide new evidence that lycopene mitigates paclitaxel-induced cognitive impairment in mice by reversing oxidative stress, endoplasmic reticulum stress, and inflammatory mechanisms.

Role of endoplasmic reticulum stress in cell apoptosis induced by duck hepatitis A virus type 1 infection

The endoplasmic reticulum (ER), an elaborate cellular organelle that interweaves the cytosol, nucleus, mitochondria and plasma membrane, is essential for cell function and survival. Disruption of ER function can trigger unfolded protein response (UPR), which is activated by ER stress (ERS). In this study, we investigated the role of ERS in cell apoptosis induced by duck hepatitis A virus type 1 (DHAV-1) infection. Our findings revealed that DHAV-1 infection led to the activation of ERS. Specially, the expression of glucose-regulated protein 78 (GRP78) was upregulated, activating two pathways of UPR: the protein kinase R-like ER kinase (PERK) pathway and the inositol-requiring enzyme 1(IRE1) pathway. Consequently, phosphorylation of eukaryotic initiation factor 2 alpha (p-eIF2α) was increased, and transcription factor 4 (ATF4) was up-regulated, resulting in the induction of the apoptotic C/EBP homologous protein (CHOP). DHAV-1-infected cells exhibited various apoptotic phenotypes, including growth arrest, induction of the DNA damage-inducible protein 34 (GADD34), activation of caspase-3, and suppression of antiapoptotic protein B cell lymphoma-2 (Bcl-2). Importantly, inhibition of PERK or protein kinase R (PKR) activity suppressed CHOP activation and DHAV-1 replication, indicating that the PERK/PKR-eIF2α pathway played a crucial role in ERS-induced apoptosis. Collectively, our study provides novel insights into the mechanism of DHAV-1-induced apoptosis and reveals a potential defense mechanism against DHAV-1 replication.

Clemastine fumarate alleviates endoplasmic reticulum stress through the Nur77/GFPT2/CHOP pathway after ischemia/reperfusion in rat hearts

BACKGROUND AND PURPOSE

Clemastine fumarate (CLE) is an H1 receptor (H1R) antagonist that is used clinically to treat various allergic disorders. It blocks histamine release from mast cells and inhibits H1R. Preliminary studies have shown that CLE can reduce myocardial ischemia/reperfusion (I/R) injury. In this study, we confirmed the efficacy of CLE against myocardial I/R injury using in vivo and in vitro examinations.

EXPERIMENTAL APPROACH

To test the efficacy of CLE against myocardial I/R injury, we established a rat model of myocardial hypoxia/reperfusion injury. A series of assessments were conducted to determine cardiac function, measure areas of myocardial infarction, and analyze the histopathological changes. Additionally, we developed a rat model of cardiomyocyte hypoxia/reoxygenation (H/R); in both models, we quantified the expression levels of key markers and cardiac injury-specific proteins to assess the biochemical milieu influenced by CLE treatment.

KEY RESULTS

Our findings demonstrated that CLE reduced the expression of nerve growth factor-induced gene B (Nur77), glutamine-fructose-6-phosphate transaminase 2 (GFPT2), and C/EBP homologous protein (CHOP) and decreased the area of myocardial infarction and the degree of endoplasmic reticulum stress. CLE pretreatment ameliorated abnormal fibers and myocardial edema and reduced the inflammatory cell infiltration caused by I/R injury. While Nur77 overexpression aggravated cardiac function, these effects were ameliorated by the downregulation of Nur77.

CONCLUSION AND IMPLICATIONS

We anticipate that these results validate the hypothesis that CLE mitigates apoptosis and reduces endogenous stress within myocardial cells by modulating Nur77, GFPT2, and CHOP expression. These findings elucidate the therapeutic mechanisms by which CLE alleviates myocardial I/R injury. In addition, they will serve as a new theoretical foundation for developing future treatment strategies and enhancing clinical applications in cardiac care.

IRE1 is a promising therapeutic target in pancreatic cancer

[Figure: see text].

Aging and voluntary exercise's effects on Aβ1-42 levels, endoplasmic reticulum stress factors, and apoptosis in the hippocampus of old male rats

Within the aging cortex, amyloid beta peptide (Aβ) is a crucial element of the senile plaques, a hallmark feature often observed in cases of Alzheimer's disease (AD). The UPR (unfolded protein response), a cellular mechanism for protein folding, is switched on by Aβ accumulation. Endoplasmic reticulum (ER) stress has been identified as playing a role in aging and the development of neurodegenerative diseases. The exact molecular pathways leading to perishing of cells from Aβ-induced ER stress, as well as the impact of voluntary exercise on these mechanisms, are still subjects awaiting a definitive answer yet. In the current study, 18 male Wistar rats were included: 6 young rats (3 months old; 200-250 g) in the Young Control group, and 12 old rats (18 months old; 400-430 g) randomly allocated to the Old Control and Old Exercise groups. The rat cages had running wheels for them to voluntarily run on for 8 weeks. This was followed by Western blotting, immunohistochemical staining, biochemical as well as morphological analyses. Voluntary exercise reduced Aβ1-42 deposition (P < 0.001) and inhibited the activation of caspase-8 (P < 0.001) and caspase-12 (P < 0.01), and on top of that down-regulated the expression of ATF6 (P < 0.001), CHOP (P < 0.01), and p-PERK (P < 0.05) proteins in the hippocampus of old male rats. Exercise amplified the population of Bcl-2-expressing cells and decreased the population of Bax-expressing cells in the hippocampus of the Old Exercise group (P < 0.001). Voluntary exercise inhibited the apoptotic pathways and suppressed the activation of UPR signaling pathways. Hence, voluntary exercise may be a therapeutic strategy and a promising approach to prevent AD through modulation of Aβ-induced ER stress.

Homeostasis control in health and disease by the unfolded protein response

Cells rely on the endoplasmic reticulum (ER) to fold and assemble newly synthesized transmembrane and secretory proteins - essential for cellular structure-function and for both intracellular and intercellular communication. To ensure the operative fidelity of the ER, eukaryotic cells leverage the unfolded protein response (UPR) - a stress-sensing and signalling network that maintains homeostasis by rebalancing the biosynthetic capacity of the ER according to need. The metazoan UPR can also redirect signalling from cytoprotective adaptation to programmed cell death if homeostasis restoration fails. As such, the UPR benefits multicellular organisms by preserving optimally functioning cells while removing damaged ones. Nevertheless, dysregulation of the UPR can be harmful. In this Review, we discuss the UPR and its regulatory processes as a paradigm in health and disease. We highlight important recent advances in molecular and mechanistic understanding of the UPR that enable greater precision in designing and developing innovative strategies to harness its potential for therapeutic gain. We underscore the rheostatic character of the UPR, its contextual nature and critical open questions for its further elucidation.

Inhibition of ERO1L induces autophagy and apoptosis via endoplasmic reticulum stress in colorectal cancer

Colorectal cancer (CRC) is one of the most common types of cancer with high incidence and mortality. Endoplasmic reticulum oxidoreductase 1 alpha (ERO1L) is overexpressed in CRC. This study aims to explore the role of ERO1L in CRC progression and evaluate the anti-tumor efficacy of the combination treatment of ERO1L inhibition with endoplasmic reticulum (ER) stress-inducing therapies. Herein, we found that ERO1L was elevated in CRC cell lines and patients. ER stress upregulated the expression of ERO1L, and ERO1L deficiency induced ER stress in CRC. ERO1L knockdown increased the susceptibility of CRC cells to ER stress. ERO1L contributed to the malignant phenotypes of CRC cells. Inhibition of ERO1L induced autophagy and caspase-dependent apoptosis by the induction of ER stress in CRC cells. Mechanically, the ERK1/2 pathway was involved in ERO1L knockdown-mediated apoptosis and autophagy. Combination treatment of ERO1L inhibition with ER stress-inducing agents, such as unfolded protein response (UPR)-targeting inhibitors and proteasome inhibitors, demonstrated enhanced anti-tumor capacity. In conclusion, ERO1L is overexpressed in CRC, and ERO1L deficiency induces apoptosis and autophagy via ER stress. ERO1L inhibition combined with ER stress-inducing therapies exhibits more effective anti-tumor activity against CRC. ERO1L may serve as a biomarker and therapeutic target for CRC treatment.

Alleviating heat stress-induced immune organ damage in ducks: Role of melittin

Heat stress, one of the major challenges facing the global livestock industry, can adversely affect the immune system. The present study explored the mechanisms by which melittin alleviates heat stress-induced immune organ damage. Three hundred 20-day-old male Huainan sheldrakes were randomly assigned to four groups: heat stress group (basal diet), heat stress + melittin group (I, II, III group, basal diet + 0.08, 0.12, 0.16 g/kg melittin, respectively). The ducks were subjected to heat stress for 4 h per day (temperature 36-38 °C, relative humidity 60-70%) for 15 consecutive days. The results showed that compared with the heat-stress group, melittin improved the production performance of heat-stressed ducks, significantly increased serum immune indices (immunoglobulin G and interferon-gamma) and antioxidant indices (total antioxidant capacity, superoxide dismutase (SOD), and glutathione) (P < 0.05), and significantly decreased malondialdehyde (MDA) levels (P < 0.05). Additionally, melittin increased antioxidant function (nuclear factor-erythroid 2 p45-related factor 2, glutathione peroxidase, SOD, and catalase), and immune index (interleukin-10). Meanwhile, melittin significantly reduced immune indices (inducible nitric oxide synthase and cyclooxygenase-2), heat shock protein 70 expression, and apoptosis levels (P < 0.05) in heat-stressed ducks. Consequently, supplementing heat-stressed ducks with 0.12 g/kg melittin increases serum immune function and antioxidants, alleviate heat stress-induced immune organ damage, and improve growth performance.

A multi-omic single-cell landscape of the aging mouse ovary

The ovary is one of the first organs in humans to exhibit age-related functional impairments. As an organ composed of diverse heterogeneous cell types, the ovary exhibits cell-type-specific changes during the aging process, ultimately leading to a decline in female fertility. Investigating the molecular mechanisms of ovarian aging is crucial for understanding age-related fertility dysfunction in females. In this study, we combine scRNA-seq and scATAC-seq from mouse young/aged ovaries to characterize molecular features during ovarian aging. Using the single-cell multi-omic data, we revealed the cell-type-specific transcriptional changes during the aging process in seven major ovarian cell types and identified the cis/trans-regulatory elements governing these transcriptional changes. Specifically, we uncovered the transcriptional alterations of TGF-beta signaling in mesenchymal cells and endoplasmic reticulum stress in granulosa cells of aged mouse ovaries and further identified the potential corresponding cis/trans-regulatory elements. These molecular alterations may contribute to aging-induced functional impairments in mouse ovaries. In summary, this work provides transcriptome and chromatin accessibility landscape of ovarian aging in mice, which serve as a resource for identifying the cell-type-specific molecular mechanisms underlying ovarian aging, aiding in the identification of potential diagnostic biomarkers and treatment strategies.

Impact of microplastics on the human digestive system: From basic to clinical

As a new type of pollutant, the harm caused by microplastics (MPs) to organisms has been the research focus. Recently, the proportion of MPs ingested through the digestive tract has gradually increased with the popularity of fast-food products, such as takeout. The damage to the digestive system has attracted increasing attention. We reviewed the literature regarding toxicity of MPs and observed that they have different effects on multiple organs of the digestive system. The mechanism may be related to the toxic effects of MPs themselves, interactions with various substances in the biological body, and participation in various signaling pathways to induce adverse reactions as a carrier of toxins to increase the time and amount of body absorption. Based on the toxicity mechanism of MPs, we propose specific suggestions to provide a theoretical reference for the government and relevant departments.

Ursodeoxycholic Acid Alleviates Palmitic Acid-Induced Apoptosis in Bovine Mammary Epithelial Cells

This study investigated the protective effects of ursodeoxycholic acid (UDCA) against PA-induced apoptosis in the MAC-T bovine mammary epithelial cell (bMEC) line by assessing the level of cell viability, oxidative stress indicators, and expression of endoplasmic reticulum (ER) stress markers. MAC-T cells were pretreated with UDCA at 25, 50, and 100 μM before exposure to PA at 300 μM. UDCA was noncytotoxic at these concentrations and significantly improved cell viability, which was reduced by PA. UDCA pretreatment notably decreased PA-induced expression of GRP78, XBP1s, ATF4, and CHOP mRNA, indicating reduced ER stress. Moreover, UDCA substantially lowered PA-induced reactive oxygen species production and dichlorofluorescein fluorescence intensities. Although PA treatment elevated GSSG levels and disrupted redox balance by decreasing both the total GSH/GSSG and reduced GSH/GSSG ratios, UDCA effectively counteracted these effects. Specifically, UDCA reduced PA-induced GSSG levels and restored redox balance by increasing both total and reduced GSH/GSSG ratios. These findings suggest that UDCA mitigates PA-induced apoptosis in MAC-T cells by enhancing redox homeostasis. Therefore, incorporating UDCA into dairy cow feed could help reduce PA-induced cellular stress and improve milk production during periods of negative energy balance.

Endoplasmic reticulum stress-mediated apoptosis and autophagy in osteoarthritis: From molecular mechanisms to therapeutic applications

Osteoarthritis (OA) is characterized primarily by the degeneration of articular cartilage, with a high prevalence and disability rate. The functional phenotype of chondrocytes, as the sole cell type within cartilage, is vital for OA progression. Due to the avascular nature of cartilage and its limited regenerative capacity, repair following injury poses significant challenges. Various cellular stressors, including hypoxia, nutrient deprivation, oxidative stress, and collagen mutations, can lead to the accumulation of misfolded proteins in the endoplasmic reticulum (ER), resulting in ER stress (ERS). In response to restore ER homeostasis as well as cellular vitality and function, a series of adaptive mechanisms are triggered, including the unfolded protein response, ER-associated degradation, and ER-phagy. Prolonged or severe ERS may exceed the adaptive capacity of cells, leading to dysregulation in apoptosis and autophagy-key pathogenic factors contributing to chondrocyte damage and OA progression. This review examines the relationship between ERS in OA chondrocytes and both apoptosis and autophagy in order to identify potential therapeutic targets and strategies for prevention and treatment of OA.

The Integrated Stress Response in Pancreatic Development, Tissue Homeostasis, and Cancer

Present in all eukaryotic cells, the integrated stress response (ISR) is a highly coordinated signaling network that controls cellular behavior, metabolism, and survival in response to diverse stresses. The ISR is initiated when any 1 of 4 stress-sensing kinases (protein kinase R-like endoplasmic reticulum kinase [PERK], general control non-derepressible 2 [GCN2], double-stranded RNA-dependent protein kinase [PKR], heme-regulated eukaryotic translation initiation factor 2α kinase [HRI]) becomes activated to phosphorylate the protein translation initiation factor eukaryotic translation initiation factor 2α (eIF2α), shifting gene expression toward a comprehensive rewiring of cellular machinery to promote adaptation. Although the ISR has been shown to play an important role in the homeostasis of multiple tissues, evidence suggests that it is particularly crucial for the development and ongoing health of the pancreas. Among the most synthetically dynamic tissues in the body, the exocrine and endocrine pancreas relies heavily on the ISR to rapidly adjust cell function to meet the metabolic demands of the organism. The hardwiring of the ISR into normal pancreatic functions and adaptation to stress may explain why it is a commonly used pro-oncogenic and therapy-resistance mechanism in pancreatic ductal adenocarcinoma and pancreatic neuroendocrine tumors. Here, we review what is known about the key roles that the ISR plays in the development, homeostasis, and neoplasia of the pancreas.

PTGS2/GRP78 Activation Triggers Endoplasmic Reticulum Stress Leading to Lipid Metabolism Disruption and Cell Apoptosis, Exacerbating Damage in Bovine Mastitis

Lipoteichoic acid (LTA), an organic acid of Gram-positive bacteria, is closely related to mastitis in dairy cows. This study evaluates the effect of LTA-induced endoplasmic reticulum stress (ER stress) in vitro using MAC-T (mammary epithelial cells) and in dairy cows with mastitis. LTA stimulation significantly increases ER stress and apoptosis-related factors in MAC-T. Further analysis suggests that the increase in ER stress may be associated with interactions involving PTGS2 and GRP78. Protein structural studies indicate a strong interaction between PTGS2 and GRP78. Lipidomics results further demonstrate that LTA disrupts lipid balance in MAC-T cells, affecting lipid metabolism in the endoplasmic reticulum, including PC, PE, TAG, and DAG, thereby exacerbating inflammation and ER stress. In dairy cows with mastitis caused by Gram-positive bacterial infection, damaged epithelial cells, inflammatory cell infiltration, and apoptotic vesicles are observed in affected tissues. In contrast, tissues from healthy cows exhibit regular epithelial cells without inflammatory cells or apoptotic vesicles. Furthermore, a significant ER stress and apoptosis increase is observed in mastitis tissues. This study demonstrates the close association between LTA-induced cell damage and ER stress, contributing to understanding the mechanisms underlying LTA-induced damage and supporting strategies for mastitis prevention and control in dairy cows.

Protection of beta cells against cytokine-induced apoptosis by the gut microbial metabolite butyrate

Type 1 diabetes (T1D) is characterized by immune cell infiltration in the islets of Langerhans, leading to the destruction of insulin-producing beta cells. This destruction is driven by secreted cytokines and cytotoxic T cells inducing apoptosis in beta cells. Butyrate, a metabolite produced by the gut microbiota, has been shown to have various health benefits, including anti-inflammatory and anti-diabetic effects. In this study, we investigated the potential protective effects of butyrate on cytokine-induced apoptosis in beta cells and explored the underlying mechanisms. Insulin-secreting INS-1E cells and isolated mouse islets were treated with interleukin-1beta (IL-1β) or a combination of IL-1β and interferon-gamma (IFN-γ) in the presence or absence of butyrate. We analyzed apoptosis, nitric oxide (NO) levels, expression of stress-related genes, and immune cell migration. Our results demonstrated that butyrate significantly attenuated cytokine-induced apoptosis in both INS-1E cells and mouse islets, accompanied by a reduction in NO levels. Butyrate also decreased the expression of endoplasmic reticulum (ER) stress markers such as Chop, phosphorylated eIF2α and Atf4, as well as some pro-apoptotic genes including Dp5 and Puma. Butyrate reduced the cytokine-induced expression of the chemokine genes Cxcl1 and Cxcl10 in mouse islets, as well as the chemotactic activity of THP-1 monocytes toward conditioned media from IL-1β-exposed islets. In conclusion, these findings indicate that butyrate protects beta cells from cytokine-induced apoptosis and ER stress, suggesting its potential as a therapeutic agent to prevent beta cell destruction in T1D.

Maternal riboflavin deficiency causes embryonic defects by activating ER stress-induced hepatocyte apoptosis pathway

Riboflavin deficiency (RD) induces liver damage, abnormal embryonic development, and high mortality. We hypothesized that the phenotype could be rescued by inhibiting ER stress. The objectives of the present study were to investigate the underlying molecular mechanisms of RD-induced embryonic defects using in vitro and in vivo models. Primary duck embryonic hepatocytes were treated with an ER stress inhibitor (4-PBA) or transfected with CHOP siRNA, and cultured in RD medium and riboflavin-sufficient (CON) medium for 8 days. Laying ducks (n = 20 cages/diet, 1 bird/cage) were fed an RD diet or CON diet for 14 wk, and the eggs were collected for hatching. At day 7 of incubation, the fertilized RD eggs were injected with or without 4-PBA into the yolk. RD decreased cell number and cell viability compared to the CON group, induced oxidative stress and apoptosis in primary duck embryonic hepatocytes. However, after being treated with an ER stress inhibitor (4-PBA) or transfected with CHOP siRNA, the apoptosis rate in RD hepatocytes decreased by 60.6 % and 86.1 %, respectively, being equal to the CON. These results indicated that RD-induced hepatocyte apoptosis is mediated by ER stress and the CHOP pathway. In vivo, RD embryos showed low hatchability, abnormal development, liver damage, ER stress, and apoptosis compared to the CON group. However, 4-PBA administration, as a model of ER stress inhibition, substantially restored embryonic development and alleviated liver damage in the RD group, including ER stress and apoptosis. Notably, hatchability in the RD group increased from 21.7 % to 72.7 % after 4-PBA treatment, though it remained less than the CON group (87.7 %). These results implicated ER stress-CHOP-apoptosis pathway as molecular mechanisms underlying RD-induced abnormal embryonic development and death, this target with potential for therapy or intervention.

Ortho-silicic Acid Prevents Glucocorticoid-Induced Femoral Head Necrosis by Promoting Akt Phosphorylation to Inhibit Endoplasmic Reticulum Stress-Mediated Apoptosis and Enhance Angiogenesis and Osteogenesis

Glucocorticoid-induced osteonecrosis of the femoral head (SONFH) is the most prevalent form of secondary osteonecrosis affecting the femoral head. Glucocorticoids can cause damage to both vascular endothelial cells and osteoblasts. Previous studies have demonstrated that silicon can improve the resistance of vascular endothelial cells to oxidative stress and positively impact bone health. However, the impact of silicon on SONFH has yet to be investigated. We examined the influence of ortho-silicic acid (OSA, Si(OH)4) on the apoptosis and proliferation of vascular endothelial cells after glucocorticoid induction. Additionally, we evaluated the expression of apoptosis-related genes such as cleaved-caspase-3, Bcl-2 and Bax. The impact of glucocorticoids and OSA on the function of vascular endothelial cells was evaluated through wound healing, transwell and angiogenesis assays. Osteogenic function was subsequently evaluated through alizarin red staining, alkaline phosphatase staining and expression levels of osteogenic genes like RUNX2 and ALP. Moreover, we investigated the potential role of OSA in vivo using the SONFH animal model. At concentrations below 100 μM, OSA exhibits no toxicity on vascular endothelial cells and effectively reverses glucocorticoid-induced apoptosis in these cells. OSA increases the resilience of vascular endothelial cells against oxidative stress and enhances osteoblast differentiation. Our study revealed that glucocorticoids activate endoplasmic reticulum stress, a process that mediates the apoptosis of vascular endothelial cells. OSA ameliorated the endoplasmic reticulum stress associated with glucocorticoids through the increased expression of p-Akt levels. In vivo, OSA treatment effectively improved SONFH by enhancing vascular endothelial cell function and promoting osteogenic differentiation. OSA counteracted the adverse effects of glucocorticoids both in vitro and in vivo, demonstrating a beneficial therapeutic effect on SONFH.

Endoplasmic reticulum stress: The underlying mechanism of chronic pain

Chronic pain (CP) affects over 30 % of the global population, imposing significant financial burdens on individuals and society. However, existing treatments for CP offer limited efficacy and troublesome side effects, primarily owing to a lack of knowledge of its precise underlying mechanism. Pathological stimuli disrupt the intricate process of protein folding and endoplasmic reticulum (ER) homeostasis. This disruption leads to the accumulation of misfolded or unfolded proteins in the ER, generating a condition termed ER stress. Emerging data have indicated that ER stress, occurring in the peripheral and central nervous systems, contributes to the development and maintenance of CP. This review aimed to comprehensively explore the intersection of ER stress and CP within the lower and upper nervous systems and highlight the cell-specific contributions of the unfolded protein response in different CP types. We provide a comprehensive synthesis of evidence from animal models, examining neuronal and non-neuronal mechanisms and discuss the damaging ER stress-linked inflammation, autophagy, oxidative stress, and apoptosis, which collectively drive disease progression and contribute to a neurotoxic environment. However, the mechanisms through which ER stress influences the most advanced centre-of-pain projections in the brain remain unclear. Further investigation in this area is crucial to elucidate the relationship between ER stress and CP and facilitate the development of novel therapeutic drugs for this intractable dilemma.

H2S alleviated sepsis-induced acute kidney injury by inhibiting PERK/Bax-Bcl2 pathway

To investigate the protective mechanisms of hydrogen sulfide (H2S) in sepsis-induced acute kidney injury (SAKI), we conducted an in vivo study using a SAKI mouse model induced by intraperitoneal lipopolysaccharide (LPS) injection. Following 6 h of LPS injection, levels of tumor necrosis factor-alpha (TNF-α) and blood urea nitrogen (Bun) were significantly elevated in mouse plasma. In the kidneys of SAKI mice, expression of H2S-generating enzymes cysteinyl-tRNA synthetase (CARS), cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS) was markedly downregulated, while glucose-regulated protein 78 (GRP78), activating transcription factor 6 (ATF6), phosphorylated protein kinase R-like endoplasmic reticulum kinase/protein kinase R-like endoplasmic reticulum kinase (p-PERK/PERK), and B-cell lymphoma-2 recombinant protein X/B-cell lymphoma-2 (Bax/Bcl2) expression was significantly upregulated. H2S improved renal function and attenuated renal histopathological changes in SAKI mice, thereby alleviating LPS-induced endoplasmic reticulum stress (ERS). Additionally, it inhibited the expression of p-PERK/PERK and Bax/Bcl2. After inhibiting CSE activity with dl-propargylglycine (PPG i. p.), the renal tissue pathology in LPS-induced AKI mice was further exacerbated, leading to enhanced activation of the PERK/Bax-Bcl2 pathway. Our findings suggest that endogenous H2S influences the pathogenesis of SAKI, while exogenous H2S protects against LPS-induced AKI by inhibiting the PERK/Bax-Bcl2 pathway involved in ERS.

Repurposing Aprepitant: Can it protect against doxorubicin-induced Chemobrain beyond its antiemetic role?

The substance P (SP) and neurokinin-1 receptor (NK-1R) axis is crucial in numerous pathological processes, including inflammation, stress responses, pain perception, and vomiting. Consequently, aprepitant, an NK-1R blocker, is used as an antiemetic in chemotherapy, including the use of doxorubicin (DOX), but whether aprepitant can also assuage DOX-mediated chemobrain remains to be unveiled. Here, we scrutinized the potential neuroprotective effect and underlying mechanisms of aprepitant using DOX-induced chemobrain model, where rats were allocated into 4 groups (control, aprepitant, DOX, and DOX+ aprepitant). Cognitive deficits were assessed through behavioral tests and hippocampal structural alterations were determined by H&E and toluidine blue staining. Biochemical measurements were performed using ELISA, real-time quantitative PCR, western blotting, and immunohistochemical methods. Aprepitant improved cognitive responses, and hippocampal morphology, enhancing the presence of intact neurons. At the molecular tier, aprepitant significantly reduced hippocampal contents of SP and the inflammatory markers NF-κB and IL-1β. Additionally, it signified its antioxidant and antiapoptotic capacities by downregulating cleaved caspase-3 protein expression and curbing the content of malondialdehyde but boosted those of glutathione and Bcl-2. Aprepitant also downregulated the expression of miR-146a and turned off the endoplasmic reticulum (ER) stress cascade PERK/eIF-2α/ATF-4/CHOP. To recapitulate, aprepitant demonstrates a neuroprotective effect against DOX-mediated chemobrain by alleviating inflammatory, oxidative, and apoptotic responses, partly by reducing SP, ER stress, and miR-146a. These findings not only underscore the potential of aprepitant as a neuroprotective agent but also offer new understanding of the mechanisms behind chemobrain, leading to better therapeutic strategies for cancer patients.

Reduced expression of NUPR1 alleviates epilepsy progression via attenuating ER stress

Epilepsy is a neurological disorder characterized by recurring seizures. It is necessary to further understand the mechanisms of epilepsy in order to develop novel strategies for its prevention and treatment. Abnormal endoplasmic reticulum stress (ERS) activation is related to the pathogenesis of epilepsy. Nuclear protein 1, transcriptional regulator (NUPR1) is involved in ERS and it might play a role in epilepsy progression. In the present study, we generated an epileptic mouse model using pilocarpine induction. After 72 h of pilocarpine treatment, the expression of NUPR1 was increased in epileptic mice. Furthermore, NUPR1 knockdown reduced the number of spontaneous recurrent seizures and alleviated hippocampal damage in these mice. Interestingly, NUPR1 knockdown also reduced the protein expression levels of LC3, PINK1, and Parkin in the mitochondria, and decreased the PINK1 expression in hippocampus. Additionally, the expression of ERS-related proteins-cleaved caspase-12, ATF4, and CHOP-decreased in epileptic mice following NUPR1 knockdown. In vitro experiments showed that the absence of NUPR1 reduced the expression of ATF4, CHOP, and cleaved caspase-12 in hippocampal neurons and inhibited the neuron apoptosis. In all, our study suggested that NUPR1 maybe a potential molecular target for epilepsy therapy.

Fragility of ER homeostatic regulation underlies haploid instability in human somatic cells

Mammalian somatic cells are generally unstable in the haploid state, resulting in haploid-to-diploid conversion within a short time frame. However, cellular and molecular principles that limit the sustainability of somatic haploidy remain unknown. In this study, we found the haploidy-linked vulnerability to endoplasmic reticulum (ER) stress as a critical cause of haploid intolerance in human somatic cells. Pharmacological induction of ER stress selectively induced apoptosis in haploid cells, facilitating the replacement of haploids by coexisting diploidized cells in a caspase-dependent manner. Biochemical analyses revealed that unfolded protein response (UPR) was activated with similar dynamics between haploids and diploids upon ER stress induction. However, haploids were less efficient in solving proteotoxic stress, resulting in a bias toward a proapoptotic mode of UPR signaling. Artificial replenishment of chaperone function substantially alleviated the haploidy-linked upregulation of proapoptotic signaling and improved haploid cell retention under tunicamycin-induced ER stress. These data demonstrate that the ER stress-driven haploid instability stems from inefficient proteostatic control that alters the functionality of UPR to cause apoptosis selectively in haploids. Interestingly, haploids suffered a higher level of protein aggregation even in unperturbed conditions, and the long-term stability of the haploid state was significantly improved by alleviating their natural proteotoxicity. Based on these results, we propose that the haploidy-specific vulnerability to ER stress creates a fundamental cause of haploid intolerance in mammalian somatic cells. Our findings provide new insight into the principle that places a stringent restriction on the evolution of animal life cycles.

The Role of Endoplasmic Reticulum Stress on Reducing Recombinant Protein Production in Mammalian Cells

Therapeutic recombinant protein production relies on industrial scale culture of mammalian cells to produce active proteins in quantities sufficient for clinical use. The combination of stresses from industrial cell culture environment and recombinant protein production can overwhelm the protein synthesis machinery in the endoplasmic reticulum (ER). This leads to a buildup of improperly folded proteins which induces ER stress. Cells respond to ER stress by activating the Unfolded Protein Response (UPR). To restore proteostasis, ER sensor proteins reduce global protein synthesis and increase chaperone protein synthesis, and if that is insufficient the proteins are degraded. If proteostasis is still not restored, apoptosis is initiated. Increasing evidence suggests crosstalk between ER proteostasis and DNA damage repair (DDR) pathways. External factors (e.g., metabolites) from the cellular environment as well as internal factors (e.g., transgene copy number) can impact genome stability. Failure to maintain genome integrity reduces cell viability and in turn protein production. This review focuses on the association between ER stress and processes that affect protein production and secretion. The processes mediated by ER stress, including inhibition of global protein translation, chaperone protein production, degradation of misfolded proteins, DNA repair, and protein secretion, impact recombinant protein production. Recombinant protein production can be reduced by ER stress through increased autophagy and protein degradation, reduced protein secretion, and reduced DDR response.

Endoplasmic reticulum stress and associated apoptosis are linked with the pathogenesis of white striping in broiler breast muscles

White striping (WS) that appears as white stripes parallel to the muscle fibrils is an emerging growth-related abnormality of broiler breast meat. The pathomechanism of this defect has not been fully understood despite intensive studies over the past decade. In the present study, endoplasmic reticulum (ER) stress and its associated apoptotic pathways were investigated to elucidate the potential role of these pathways in the development of WS. To this end, a total of 60 Pectoralis major (Pm) muscle samples were collected from 55-d-old Ross 308 male broiler chickens according to the severity of gross WS lesions (normal, mild, and severe). Histopathological and molecular analyses were conducted to evaluate the lesions and genes involved in the ER stress and related apoptosis. All the Pm samples, both with and without macroscopic WS lesions, showed varying degrees of myodegenerative lesions. Molecular analysis revealed that the transcript abundances of many components related to protein kinase R-like ER kinase (PERK) and inositol-requiring enzyme type 1 (IRE-1) signals of the ER stress response were significantly greater in severely WS-affected breast tissues compared to their mildly affected and normal counterparts. Similarly, the transcript abundances of apoptotic markers related to both signaling pathways were significantly greater in severe WS lesions than those of mildly affected and normal Pm tissues. Besides these, a significant increase in caspase-3 transcript abundance was seen in severe WS lesions in comparison with mild WS and normal breast muscles. Findings of this study suggest that ER stress response and its related apoptotic pathways are possibly activated in the breast muscle of broiler chickens with severe WS lesions. Based on these findings, it is speculated that ER stress-mediated apoptosis occupies a central role in the progression of WS in broiler chickens.

Mechanisms of ferroptosis and the relationship between ferroptosis and ER stress after JEV and HSV infection

Ferroptosis is a novel form of programmed cell death, which is different from apoptosis, pyroptosis and autophagy in morphology and biochemistry. Ferroptosis is characterized by condensed mitochondrial membrane densities, vanished of mitochondria crista and outer membrane rupture in morphology, and the accumulation of intracellular iron, lipid peroxidation (LPO), decrease of GSH and inhibition of GPX4 in biochemistry. Japanese encephalitis virus (JEV) and Herpes simplex virus (HSV) are both common neurotropic viruses that can cause neurological disorders, such as severe encephalitis. JEV and HSV have been demonstrated to be able to induce ferroptosis. This process is closely related to the inhibition of the GSH-GPX4 system, ACSL4 phosphorylation, and Nrf2 ubiquitination. In this review, we summarized the mechanisms by which JEV and HSV induced ferroptosis in the current study. In addition, we found a strong relationship between endoplasmic reticulum (ER) stress and ferroptosis, and we therefore speculated that sustained ER stress might be a prerequisite for ferroptosis in JEV and HSV-induced diseases.

Endoplasmic reticulum stress response pathway-mediated cell death in ovarian cancer

The endoplasmic reticulum (ER) is one of the largest organelles, and Endoplasmic Reticulum Stress Response Pathway is a series of responses triggered by the homeostatic imbalance of the ER and the state in which unfolded or misfolded proteins accumulate in the ER, which can trigger cell death. Cell death plays a crucial role in the development of diseases such as gynecological oncology. Herein, we review the current research on the response and ovarian cancer, discussing the key sensors (IRE1, PERK, ATF6), and the conditions under which it occurs (Ca2+ homeostasis disruption, hypoxia, others). Using the response as a starting point, provide a comprehensive overview of the relationship with the four types of cell death (apoptosis, autophagy, immunogenic cell death, paraptosis) in an attempt to provide new targeted therapeutic strategies for the organelle-Endoplasmic Reticulum Stress Response Pathway-cell death in ovarian cancer therapy.

Novel WFS1 variants are associated with different diabetes phenotypes

Background

The WFS1 gene encodes the protein wolframin, which is crucial for maintaining endoplasmic reticulum homeostasis. Variants in this gene are predominantly associated with Wolfram syndrome and have been implicated in other disorders such as diabetes mellitus and psychiatric diseases, which increases the rate of clinical misdiagnosis.

Methods

Patients were diagnosed with early-onset unclassified diabetes according to their clinical and laboratory data. We performed whole-exome sequencing (WES) in 165 patients, interpreting variants according to the American College of Medical Genetics/Association for Molecular Pathology (ACMG/AMP) 2015 guidelines. Variant verification was done by Sanger sequencing. In vitro experiments were conducted to evaluate the effects of WFS1 compound heterozygous variants.

Results

We identified WFS1 compound heterozygous variants (p.A214fs*74/p.F329I and p.I427S/p.I304T) in two patients with Wolfram Syndrome-Like disorders (WSLD). Both WFS1 compound heterozygous variants were associated with increased ER stress, reduced cell viability, and decreased SERCA2b mRNA levels. Additionally, pathogenic or likely pathogenic WFS1 heterozygous variants were identified in the other three patients.

Conclusion

Our results underscore the importance of early genetic testing for diagnosing young-onset diabetes and highlight the clinical relevance of WFS1 variants in increasing ER stress and reducing cell viability. Incorporating these genetic insights into clinical practice can reduce misdiagnoses and improve treatment strategies for related disorders.

Navigating the landscape of the unfolded protein response in CD8+ T cells

Endoplasmic reticulum stress occurs due to large amounts of misfolded proteins, hypoxia, nutrient deprivation, and more. The unfolded protein is a complex intracellular signaling network designed to operate under this stress. Composed of three individual arms, inositol-requiring enzyme 1, protein kinase RNA-like ER kinase, and activating transcription factor-6, the unfolded protein response looks to resolve stress and return to proteostasis. The CD8+ T cell is a critical cell type for the adaptive immune system. The unfolded protein response has been shown to have a wide-ranging spectrum of effects on CD8+ T cells. CD8+ T cells undergo cellular stress during activation and due to environmental insults. However, the magnitude of the effects this response has on CD8+ T cells is still understudied. Thus, studying these pathways is important to unraveling the inner machinations of these powerful cells. In this review, we will highlight the recent literature in this field, summarize the three pathways of the unfolded protein response, and discuss their roles in CD8+ T cell biology and functionality.

TXNDC5 Plays a Crucial Role in Regulating Endoplasmic Reticulum Activity through Different ER Stress Signaling Pathways in Hepatic Cells

The pathogenesis of non-alcoholic fatty liver disease (NAFLD) is influenced by a number of variables, including endoplasmic reticulum stress (ER). Thioredoxin domain-containing 5 (TXNDC5) is a member of the protein disulfide isomerase family and acts as an endoplasmic reticulum (ER) chaperone. Nevertheless, the function of TXNDC5 in hepatocytes under ER stress remains largely uncharacterized. In order to identify the role of TXNDC5 in hepatic wild-type (WT) and TXNDC5-deficient (KO) AML12 cell lines, tunicamycin, palmitic acid, and thapsigargin were employed as stressors. Cell viability, mRNA, protein levels, and mRNA splicing were then assayed. The protein expression results of prominent ER stress markers indicated that the ERN1 and EIF2AK3 proteins were downregulated, while the HSPA5 protein was upregulated. Furthermore, the ATF6 protein demonstrated no significant alterations in the absence of TXNDC5 at the protein level. The knockout of TXNDC5 has been demonstrated to increase cellular ROS production and its activity is required to maintain normal mitochondrial function during tunicamycin-induced ER stress. Tunicamycin has been observed to disrupt the protein levels of HSPA5, ERN1, and EIF2AK3 in TXNDC5-deficient cells. However, palmitic acid has been observed to disrupt the protein levels of ATF6, HSPA5, and EIF2AK3. In conclusion, TXNDC5 can selectively activate distinct ER stress pathways via HSPA5, contingent on the origin of ER stress. Conversely, the absence of TXNDC5 can disrupt the EIF2AK3 cascade.

Molecular Mechanisms of the Therapeutic Effect of Selenium Nanoparticles in Hepatocellular Carcinoma

This review describes and summarizes, for the first time, the molecular mechanisms of the cytotoxic effect of selenium nanoparticles of various origins on hepatocellular carcinoma cells. The text provides information from recent years indicating the regulation of various signaling pathways and endoplasmic reticulum stress by selenium nanoparticles; the pathways of cell death of liver cancer cells as a result of exposure to selenium nanoparticles are considered. Particular attention is paid to the participation of selenoproteins and selenium-containing thioredoxin reductases and glutathione peroxidases in these processes. Previously, there were no reviews that fully reflected the cytotoxic effects of selenium nanoparticles specifically in hepatocellular carcinoma, despite the fact that many reviews and experimental articles have been devoted to the causes of this disease and the molecular mechanisms of regulation of cytotoxic effects by other agents. The relevance of this review is primarily explained by the fact that despite the development of various drugs and approaches for the treatment and prevention of hepatocellular carcinoma, this disease is still the fourth leading cause of death in the world. For this reason, a complete understanding of the latest trends in the treatment of oncology of various etiologies, especially hepatocellular carcinoma, is extremely important.

Green Synthesized Zinc Oxide Nanoparticles Attenuate Acrylamide-Induced Cardiac Injury via Controlling Endoplasmic Reticulum Stress-Associated Apoptosis Through ATF3/CHOP/BCL2 Signaling in Rats

Due to their distinctive properties, several eco-friendly metal oxide nanoparticles were assessed for their possible cardioprotective properties. Acrylamide (ACD), a pervasive chemical in food and the environment, has been linked to cardiac toxicity. Therefore, this study examined the probable protective effect of green synthesized zinc oxide nanoparticles (GS-ZNPs) against ACD-oral exposure-induced cardiac damage in rats. For 60 days, 40 male Sprague-Dawley rats were separated into four sets that orally administered distilled water, 10-mg GS-ZNP/kg b.w., 20-mg ACD/kg b.w., or GS-ZNP + ACD. Then, cardiac damage indicators comprising CPK, CK-MB, cTn, and LDH were assessed. Besides, cardiac tissues' architecture, oxidative stress indicators, and Zn content were evaluated. The mRNA expression of the ERS-related genes, including ATF3, ATF4, ATF6, XBP-1, CHOP, JNKs, and BiP, were determined. Moreover, ERS-dependent anti-apoptotic (BCL-2) and apoptotic (Caspase-3 and BAX) genes mRNA expression were analyzed. The results showed that GS-ZNP significantly alleviated the increased ACD-induced serum cardiac damage indicators, MDA tissue content, and histopathological changes. Furthermore, the ACD-induced reduction of antioxidants and Zn heart contents were significantly reestablished by GS-ZNP. Furthermore, the ACD-induced upregulation of the ERS-encoding genes and apoptotic genes was reversed by GS-ZNP. Besides, the ACD-induced BCL-2 downregulation was counteracted by GS-ZNP. Overall, GS-ZNP could be a biologically potent compound to alleviate ACD's cardiotoxic effects, possibly by controlling the ERS and apoptosis-related genes and antioxidant activity.

Endoplasmic Reticulum Stress in Hypertension and Salt Sensitivity of Blood Pressure

PURPOSE OF REVIEW

Hypertension is a principal risk factor for cardiovascular morbidity and mortality, with its severity exacerbated by high sodium intake, particularly in individuals with salt-sensitive blood pressure. However, the mechanisms underlying hypertension and salt sensitivity are only partly understood. Herein, we review potential interactions in hypertension pathophysiology involving the immune system, endoplasmic reticulum (ER) stress, the unfolded protein response (UPR), and proteostasis pathways; identify knowledge gaps; and discuss future directions.

RECENT FINDINGS

Recent advancements by our research group and others reveal interactions within and between adaptive and innate immune responses in hypertension pathophysiology. The salt-immune-hypertension axis is further supported by the discovery of the role of dendritic cells in hypertension, marked by isolevuglandin (IsoLG) formation. Alongside these broadened understandings of immune-mediated salt sensitivity, the contributions of T cells to hypertension have been recently challenged by groups whose findings did not support increased resistance of Rag-1-deficient mice to Ang II infusion. Hypertension has also been linked to ER stress and the UPR. Notably, a holistic approach is needed because the UPR engages in crosstalk with autophagy, the ubiquitin proteasome, and other proteostasis pathways, that may all involve hypertension. There is a critical need for studies to establish cause and effect relationships between ER stress and the UPR in hypertension pathophysiology in humans and to determine whether the immune system and ER stress function mainly to exacerbate or initiate hypertension and target organ injury. This review of recent studies proposes new avenues for future research for targeted therapeutic interventions.

Endoplasmic reticulum stress in pancreatic β-cell dysfunction: The potential therapeutic role of dietary flavonoids

Diabetes mellitus (DM) is a global health burden that is characterized by the loss or dysfunction of pancreatic β-cells. In pancreatic β-cells, endoplasmic reticulum (ER) stress is a fact of life that contributes to β-cell loss or dysfunction. Despite recent advances in research, the existing treatment approaches such as lifestyle modification and use of conventional therapeutics could not prevent the loss or dysfunction of pancreatic β-cells to abrogate the disease progression. Therefore, targeting ER stress and the consequent unfolded protein response (UPR) in pancreatic β-cells may be a potential therapeutic strategy for diabetes treatment. Dietary phytochemicals have therapeutic applications in human health owing to their broad spectrum of biochemical and pharmacological activities. Flavonoids, which are commonly obtained from fruits and vegetables worldwide, have shown promising prospects in alleviating ER stress. Dietary flavonoids including quercetin, kaempferol, myricetin, isorhamnetin, fisetin, icariin, apigenin, apigetrin, vitexin, baicalein, baicalin, nobiletin hesperidin, naringenin, epigallocatechin 3-O-gallate hesperidin (EGCG), tectorigenin, liquiritigenin, and acacetin have shown inhibitory effects on ER stress in pancreatic β-cells. Dietary flavonoids modulate ER stress signaling components, chaperone proteins, transcription factors, oxidative stress, autophagy, apoptosis, and inflammatory responses to exert their pharmacological effects on pancreatic β-cells ER stress. This review focuses on the role of dietary flavonoids as potential therapeutic adjuvants in preserving pancreatic β-cells from ER stress. Highlights of the underlying mechanisms of action are also presented as well as possible strategies for clinical translation in the management of DM.

Loss of TRIM29 mitigates viral myocarditis by attenuating PERK-driven ER stress response in male mice

Viral myocarditis, an inflammatory disease of the myocardium, is a significant cause of sudden death in children and young adults. The current coronavirus disease 19 pandemic emphasizes the need to understand the pathogenesis mechanisms and potential treatment strategies for viral myocarditis. Here, we found that TRIM29 was highly induced by cardiotropic viruses and promoted protein kinase RNA-like endoplasmic reticulum kinase (PERK)-mediated endoplasmic reticulum (ER) stress, apoptosis, and reactive oxygen species (ROS) responses that promote viral replication in cardiomyocytes in vitro. TRIM29 deficiency protected mice from viral myocarditis by promoting cardiac antiviral functions and reducing PERK-mediated inflammation and immunosuppressive monocytic myeloid-derived suppressor cells (mMDSC) in vivo. Mechanistically, TRIM29 interacted with PERK to promote SUMOylation of PERK to maintain its stability, thereby promoting PERK-mediated signaling pathways. Finally, we demonstrated that the PERK inhibitor GSK2656157 mitigated viral myocarditis by disrupting the TRIM29-PERK connection, thereby bolstering cardiac function, enhancing cardiac antiviral responses, and curbing inflammation and immunosuppressive mMDSC in vivo. Our findings offer insight into how cardiotropic viruses exploit TRIM29-regulated PERK signaling pathways to instigate viral myocarditis, suggesting that targeting the TRIM29-PERK axis could mitigate disease severity.

ER stress signaling at the interphase between MASH and HCC

HCC is the most frequent primary liver cancer with an extremely poor prognosis and often develops on preset of chronic liver diseases. Major risk factors for HCC include metabolic dysfunction-associated steatohepatitis, a complex multifactorial condition associated with abnormal endoplasmic reticulum (ER) proteostasis. To cope with ER stress, the unfolded protein response engages adaptive reactions to restore the secretory capacity of the cell. Recent advances revealed that ER stress signaling plays a critical role in HCC progression. Here, we propose that chronic ER stress is a common transversal factor contributing to the transition from liver disease (risk factor) to HCC. Interventional strategies to target the unfolded protein response in HCC, such as cancer therapy, are also discussed.

ER stress and the unfolded protein response in gastrointestinal stem cells and carcinogenesis

Endoplasmic reticulum (ER) stress and the adaptive response that follows, termed the unfolded protein response (UPR), are crucial molecular mechanisms to maintain cellular integrity by safeguarding proper protein synthesis. Next to being important in protein homeostasis, the UPR is intricate in cell fate decisions such as proliferation, differentiation, and stemness. In the intestine, stem cells are critical in governing epithelial homeostasis and they are the cell of origin of gastrointestinal malignancies. In this review, we will discuss the role of ER stress and the UPR in the gastrointestinal tract, focusing on stem cells and carcinogenesis. Insights in mechanisms that connect ER stress and UPR with stemness and carcinogenesis may broaden our understanding in the development of cancer throughout the gastrointestinal tract and how we can exploit these mechanisms to target these malignancies.

Sphingosine-1-Phosphate Inhibition Increases Endoplasmic Reticulum Stress to Enhance Oxaliplatin Sensitivity in Pancreatic Cancer

Background

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer resistant to current therapies, including oxaliplatin (Oxa). Growing evidence supports the ability of cancers to harness sphingolipid metabolism for survival. Sphingosine-1-phosphate (S1P) is an anti-apoptotic, pro-survival mediator that can influence cellular functions such as endoplasmic reticulum (ER) stress. We hypothesize that PDAC drives dysregulated sphingolipid metabolism and that S1P inhibition can enhance ER stress to improve therapeutic response to Oxa in PDAC.

Methods

RNA sequencing data of sphingolipid mediators from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression Project (GTEx) datasets were analyzed. Murine and human PDAC cell lines were treated with small interfering RNA (siRNA) against sphingosine kinase-2 (SPHK2) or ABC294640 (ABC) and incubated with combinations of vehicle control or Oxa. In an orthotopic syngeneic KPC PDAC model, tumors were treated with either vehicle control, Oxa, ABC, or combination therapy.

Results

RNA sequencing analysis revealed multiple significantly differentially expressed sphingolipid mediators (P < 0.05). In vitro, both siRNA knockdown of SPHK2 and ABC sensitized cells to Oxa therapy (P < 0.05), and induced eukaryotic initiation factor 2α (eIF2α) and protein kinase RNA-like endoplasmic reticulum kinase (PERK) phosphorylation, hallmarks of ER stress. In vitro therapy also increased extracellular high mobility group box 1 (HMGB1) release (P < 0.05), necessary for immunogenic cell death (ICD). In vivo combination therapy increased apoptotic markers as well as the intensity of HMGB1 staining compared to control (P < 0.05).

Conclusions

Our evidence suggests that sphingolipid metabolism is dysregulated in PDAC. Furthermore, S1P inhibition can sensitize PDAC to Oxa therapy through increasing ER stress and can potentiate ICD induction. This highlights a potential therapeutic target for chemosensitizing PDAC as well as an adjunct for future chemoimmunotherapy strategies.

BCL-2 Modulates IRE1α Activation to Attenuate Endoplasmic Reticulum Stress and Pulmonary Fibrosis

BCL-2 family members are known to be implicated in survival in numerous biological settings. Here, we provide evidence that in injury and repair processes in lungs, BCL-2 mainly acts to attenuate endoplasmic reticulum (ER) stress and limit extracellular matrix accumulation. Days after an intratracheal bleomycin challenge, mice lose a fraction of their alveolar type II epithelium from terminal ER stress driven by activation of the critical ER sensor and stress effector IRE1α. This fraction is dramatically increased by BCL-2 inhibition, because IRE1α activation is dependent on its physical association with the BCL-2-proapoptotic family member BAX, and we found BCL-2 to disrupt this association in vitro. In vivo, navitoclax (a BCL-2/BCL-xL inhibitor) given 15-21 days after bleomycin challenge evoked strong activation of IRE-1α in mesenchymal cells and markers of ER stress, but not apoptosis. Remarkably, after BCL-2 inhibition, bleomycin-exposed mice demonstrated persistent collagen accumulation at Day 42, compared with resolution in controls. Enhanced fibrosis proved to be due to the RNAase activity of IRE1α downregulating MRC2 mRNA and protein, a mediator of collagen turnover. The critical role of MRC2 was confirmed in precision-cut lung slice cultures of Day-42 lungs from bleomycin-exposed wild-type and MRC2 null mice. Soluble and tissue collagen accumulated in precision-cut lung slice cultures from navitoclax-treated, bleomycin-challenged mice compared with controls, in a manner nearly identical to that of challenged but untreated MRC2 null mice. Thus, apart from mitochondrial-based antiapoptosis, BCL-2 functions to attenuate ER stress responses, fostering tissue homeostasis and injury repair.

Detection of ER Stress in iPSC-Derived Neurons Carrying the p.N370S Mutation in the GBA1 Gene

Endoplasmic reticulum (ER) stress is involved in the pathogenesis of many human diseases, such as cancer, type 2 diabetes, kidney disease, atherosclerosis and neurodegenerative diseases, in particular Parkinson's disease (PD). Since there is currently no treatment for PD, a better understanding of the molecular mechanisms underlying its pathogenesis, including the mechanisms of the switch from adaptation in the form of unfolded protein response (UPR) to apoptosis under ER stress conditions, may help in the search for treatment methods. Genetically encoded biosensors based on fluorescent proteins are suitable tools that facilitate the study of living cells and visualization of molecular events in real time. The combination of technologies to generate patient-specific iPSC lines and genetically encoded biosensors allows the creation of cell models with new properties. Using CRISPR-Cas9-mediated homologous recombination at the AAVS1 locus of iPSC with the genetic variant p.N370S (rs76763715) in the GBA1 gene, we created a cell model designed to study the activation conditions of the IRE1-XBP1 cascade of the UPR system. The cell lines obtained have a doxycycline-dependent expression of the genetically encoded biosensor XBP1-TagRFP, possess all the properties of human pluripotent cells, and can be used to test physical conditions and chemical compounds that affect the development of ER stress, the functioning of the UPR system, and in particular, the IRE1-XBP1 cascade.

KSRP improves pancreatic beta cell function and survival

Impaired insulin production and/or secretion by pancreatic beta cells can lead to high blood glucose levels and type 2 diabetes (T2D). Therefore, investigating new proteins involved in beta cell response to stress conditions could be useful in finding new targets for therapeutic approaches. KH-type splicing regulatory protein (KSRP) is a protein usually involved in gene expression due to its role in post-transcriptional regulation. Although there are studies describing the important role of KSRP in tissues closely related to glucose homeostasis, its effect on pancreatic beta cells has not been explored so far. Pancreatic islets from diet-induced obese mice (C57BL/6JUnib) were used to determine KSRP expression and we also performed in vitro experiments exposing INS-1E cells (pancreatic beta cell line) to different stressors (palmitate or cyclopiazonic acid-CPA) to induce cellular dysfunction. Here we show that KSRP expression is reduced in all the beta cell dysfunction models tested. In addition, when manipulated to knock down KSRP, beta cells exhibited increased death and impaired insulin secretion, whereas KSRP overexpression prevented cell death and increased insulin secretion. Taken together, our findings suggest that KSRP could be an important target to protect beta cells from impaired functioning and death.

Therapeutic Potential of Targeting the PERK Signaling Pathway in Ischemic Stroke

Many pathologic states can lead to the accumulation of unfolded/misfolded proteins in cells. This causes endoplasmic reticulum (ER) stress and triggers the unfolded protein response (UPR), which encompasses three main adaptive branches. One of these UPR branches is mediated by protein kinase RNA-like ER kinase (PERK), an ER stress sensor. The primary consequence of PERK activation is the suppression of global protein synthesis, which reduces ER workload and facilitates the recovery of ER function. Ischemic stroke induces ER stress and activates the UPR. Studies have demonstrated the involvement of the PERK pathway in stroke pathophysiology; however, its role in stroke outcomes requires further clarification. Importantly, considering mounting evidence that supports the therapeutic potential of the PERK pathway in aging-related cognitive decline and neurodegenerative diseases, this pathway may represent a promising therapeutic target in stroke. Therefore, in this review, our aim is to discuss the current understanding of PERK in ischemic stroke, and to summarize pharmacologic tools for translational stroke research that targets PERK and its associated pathways.

Biological mechanisms and clinical significance of endoplasmic reticulum oxidoreductase 1 alpha (ERO1α) in human cancer

A firm link between endoplasmic reticulum (ER) stress and tumors has been wildly reported. Endoplasmic reticulum oxidoreductase 1 alpha (ERO1α), an ER-resident thiol oxidoreductase, is confirmed to be highly upregulated in various cancer types and associated with a significantly worse prognosis. Of importance, under ER stress, the functional interplay of ERO1α/PDI axis plays a pivotal role to orchestrate proper protein folding and other key processes. Multiple lines of evidence propose ERO1α as an attractive potential target for cancer treatment. However, the unavailability of specific inhibitor for ERO1α, its molecular inter-relatedness with closely related paralog ERO1β and the tightly regulated processes with other members of flavoenzyme family of enzymes, raises several concerns about its clinical translation. Herein, we have provided a detailed description of ERO1α in human cancers and its vulnerability towards the aforementioned concerns. Besides, we have discussed a few key considerations that may improve our understanding about ERO1α in tumors.

Impact of Complex Apoptotic Signaling Pathways on Cancer Cell Sensitivity to Therapy

Anticancer drugs induce apoptotic and non-apoptotic cell death in various cancer types. The signaling pathways for anticancer drug-induced apoptotic cell death have been shown to differ between drug-sensitive and drug-resistant cells. In atypical multidrug-resistant leukemia cells, the c-Jun/activator protein 1 (AP-1)/p53 signaling pathway leading to apoptotic death is altered. Cancer cells treated with anticancer drugs undergo c-Jun/AP-1-mediated apoptotic death and are involved in c-Jun N-terminal kinase activation and growth arrest- and DNA damage-inducible gene 153 (Gadd153)/CCAAT/enhancer-binding protein homologous protein pathway induction, regardless of the p53 genotype. Gadd153 induction is associated with mitochondrial membrane permeabilization after anticancer drug treatment and involves a coupled endoplasmic reticulum stress response. The induction of apoptosis by anticancer drugs is mediated by the intrinsic pathway (cytochrome c, Cyt c) and subsequent activation of the caspase cascade via proapoptotic genes (e.g., Bax and Bcl-xS) and their interactions. Anticancer drug-induced apoptosis involves caspase-dependent and caspase-independent pathways and occurs via intrinsic and extrinsic pathways. The targeting of antiapoptotic genes such as Bcl-2 enhances anticancer drug efficacy. The modulation of apoptotic signaling by Bcl-xS transduction increases the sensitivity of multidrug resistance-related protein-overexpressing epidermoid carcinoma cells to anticancer drugs. The significance of autophagy in cancer therapy remains to be elucidated. In this review, we summarize current knowledge of cancer cell death-related signaling pathways and their alterations during anticancer drug treatment and discuss potential strategies to enhance treatment efficacy.

Repositioning of mifepristone as an integrated stress response activator to potentiate cisplatin efficacy in non-small cell lung cancer

Lung cancer, primarily non-small-cell lung cancer (NSCLC), is a significant cause of cancer-related mortality worldwide. Cisplatin-based chemotherapy is a standard treatment for NSCLC; however, its effectiveness is often limited due to the development of resistance, leading to NSCLC recurrence. Thus, the identification of effective chemosensitizers for cisplatin is of paramount importance. The integrated stress response (ISR), activated by various cellular stresses and mediated by eIF2α kinases, has been implicated in drug sensitivity. ISR activation globally suppresses protein synthesis while selectively promoting the translation of ATF4 mRNA, which can induce pro-apoptotic proteins such as CHOP, ATF3, and TRIB3. To expedite and economize the development of chemosensitizers for cisplatin treatment in NSCLC, we employed a strategy to screen an FDA-approved drug library for ISR activators. In this study, we identified mifepristone as a potent ISR activator. Mifepristone activated the HRI/eIF2α/ATF4 axis, leading to the induction of pro-apoptotic factors, independent of its known role as a synthetic steroid. Our in vitro and in vivo models demonstrated mifepristone's potential to inhibit NSCLC re-proliferation following cisplatin treatment and tumor growth, respectively, via the ISR-mediated cell death pathway. These findings suggest that mifepristone, as an ISR activator, could enhance the efficacy of cisplatin-based therapy for NSCLC, highlighting the potential of drug repositioning in the search for effective chemosensitizers.

Regulation of cardiac fibroblast cell death by unfolded protein response signaling

The endoplasmic reticulum (ER) is a tightly regulated organelle that requires specific environmental properties to efficiently carry out its function as a major site of protein synthesis and folding. Embedded in the ER membrane, ER stress sensors inositol-requiring enzyme 1 (IRE1), protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), and activating transcription factor 6 (ATF6) serve as a sensitive quality control system collectively known as the unfolded protein response (UPR). In response to an accumulation of misfolded proteins, the UPR signals for protective mechanisms to cope with the cellular stress. Under prolonged unstable conditions and an inability to regain homeostasis, the UPR can shift from its original adaptive response to mechanisms leading to UPR-induced apoptosis. These UPR signaling pathways have been implicated as an important feature in the development of cardiac fibrosis, but identifying effective treatments has been difficult. Therefore, the apoptotic mechanisms of UPR signaling in cardiac fibroblasts (CFs) are important to our understanding of chronic fibrosis in the heart. Here, we summarize the maladaptive side of the UPR, activated downstream pathways associated with cell death, and agents that have been used to modify UPR-induced apoptosis in CFs.

The endoplasmic reticulum: Homeostasis and crosstalk in retinal health and disease

The endoplasmic reticulum (ER) is the largest intracellular organelle carrying out a broad range of important cellular functions including protein biosynthesis, folding, and trafficking, lipid and sterol biosynthesis, carbohydrate metabolism, and calcium storage and gated release. In addition, the ER makes close contact with multiple intracellular organelles such as mitochondria and the plasma membrane to actively regulate the biogenesis, remodeling, and function of these organelles. Therefore, maintaining a homeostatic and functional ER is critical for the survival and function of cells. This vital process is implemented through well-orchestrated signaling pathways of the unfolded protein response (UPR). The UPR is activated when misfolded or unfolded proteins accumulate in the ER, a condition known as ER stress, and functions to restore ER homeostasis thus promoting cell survival. However, prolonged activation or dysregulation of the UPR can lead to cell death and other detrimental events such as inflammation and oxidative stress; these processes are implicated in the pathogenesis of many human diseases including retinal disorders. In this review manuscript, we discuss the unique features of the ER and ER stress signaling in the retina and retinal neurons and describe recent advances in the research to uncover the role of ER stress signaling in neurodegenerative retinal diseases including age-related macular degeneration, inherited retinal degeneration, achromatopsia and cone diseases, and diabetic retinopathy. In some chapters, we highlight the complex interactions between the ER and other intracellular organelles focusing on mitochondria and illustrate how ER stress signaling regulates common cellular stress pathways such as autophagy. We also touch upon the integrated stress response in retinal degeneration and diabetic retinopathy. Finally, we provide an update on the current development of pharmacological agents targeting the UPR response and discuss some unresolved questions and knowledge gaps to be addressed by future research.

DWN12088, A Prolyl-tRNA Synthetase Inhibitor, Alleviates Hepatic Injury in Nonalcoholic Steatohepatitis

BACKGRUOUND

Nonalcoholic steatohepatitis (NASH) is a liver disease caused by obesity that leads to hepatic lipoapoptosis, resulting in fibrosis and cirrhosis. However, the mechanism underlying NASH is largely unknown, and there is currently no effective therapeutic agent against it. DWN12088, an agent used for treating idiopathic pulmonary fibrosis, is a selective prolyl-tRNA synthetase (PRS) inhibitor that suppresses the synthesis of collagen. However, the mechanism underlying the hepatoprotective effect of DWN12088 is not clear. Therefore, we investigated the role of DWN12088 in NASH progression.

METHODS

Mice were fed a chow diet or methionine-choline deficient (MCD)-diet, which was administered with DWN12088 or saline by oral gavage for 6 weeks. The effects of DWN12088 on NASH were evaluated by pathophysiological examinations, such as real-time quantitative reverse transcription polymerase chain reaction, immunoblotting, biochemical analysis, and immunohistochemistry. Molecular and cellular mechanisms of hepatic injury were assessed by in vitro cell culture.

RESULTS

DWN12088 attenuated palmitic acid (PA)-induced lipid accumulation and lipoapoptosis by downregulating the Rho-kinase (ROCK)/AMP-activated protein kinase (AMPK)/sterol regulatory element-binding protein-1c (SREBP-1c) and protein kinase R-like endoplasmic reticulum kinase (PERK)/α subunit of eukaryotic initiation factor 2 (eIF2α)/activating transcription factor 4 (ATF4)/C/EBP-homologous protein (CHOP) signaling cascades. PA increased but DWN12088 inhibited the phosphorylation of nuclear factor-κB (NF-κB) p65 (Ser536, Ser276) and the expression of proinflammatory genes. Moreover, the DWN12088 inhibited transforming growth factor β (TGFβ)-induced pro-fibrotic gene expression by suppressing TGFβ receptor 1 (TGFβR1)/Smad2/3 and TGFβR1/glutamyl-prolyl-tRNA synthetase (EPRS)/signal transducer and activator of transcription 6 (STAT6) axis signaling. In the case of MCD-diet-induced NASH, DWN12088 reduced hepatic steatosis, inflammation, and lipoapoptosis and prevented the progression of fibrosis.

CONCLUSION

Our findings provide new insights about DWN12088, namely that it plays an important role in the overall improvement of NASH. Hence, DWN12088 shows great potential to be developed as a new integrated therapeutic agent for NASH.