Excessive Endoplasmic Reticulum Research Articles

Role of endoplasmic reticulum stress and autophagy in the transition from acute kidney injury to chronic kidney disease.

Acute kidney injury (AKI) and chronic kidney disease (CKD) are global health concerns with increasing rates in morbidity and mortality. Transition from AKI-to-CKD is common and requires awareness in the management of AKI survivors. AKI-to-CKD transition is a main risk factor for the development of cardiovascular disease and progression to end-stage kidney disease. The mechanisms driving AKI-to-CKD transition are being explored to identify potential molecular and cellular targets for renoprotective drug interventions. Endoplasmic reticulum (ER) stress and autophagy are involved in the process of AKI-to-CKD transition. Excessive ER stress results in the persistent activation of unfolded protein response, which is an underneath cause of kidney cell death. Moreover, ER stress modulates autophagy and vice-versa. Autophagy is a degradation defensive mechanism protecting cells from malfunction. However, the underlying pathological mechanism involved in this interplay in the context of AKI-to-CKD transition is still unclear. In this review, we discuss the crosstalk between ER stress and autophagy in AKI, AKI-to-CKD transition, and CKD progression. In addition, we explore possible therapeutic targets that can regulate ER stress and autophagy to prevent AKI-to-CKD transition to improve the long-term prognosis of AKI survivors.

Effects of folic acid on oxidative damage of kidney in lead-exposed rats.

Lead (Pb) has many applications in daily life, but in recent years, various problems caused by lead exposure have aroused people's concern. Folic acid is widely found in fruits and has received more attention for its antioxidant function. However, the role of folic acid in lead-induced kidney injury in rats is unclear. This study was designed to investigate the effects of folic acid on oxidative stress and endoplasmic reticulum stress in the kidney of rats caused by lead exposure. Forty specific pathogen-free male Rattus norvegicus rats were randomly divided into control, lead, intervention, and folic acid groups. The levels of SOD, GSH-Px, GSH, and MDA were measured by biochemical kits. The protein levels of Nrf2, HO-1, CHOP, and GRP78 were measured by immunofluorescence. This study showed that lead exposure increased the blood levels of lead in mice. However, the intervention of folic acid decreased the levels of lead, but the difference was not statistically significant. Lead exposure causes oxidative stress by decreasing kidney SOD, GSH-Px, and GSH levels and increasing MDA levels. However, folic acid alleviated the oxidative damage caused by lead exposure by increasing the levels of GSH-Px and GSH and decreasing the levels of MDA. Immunofluorescence results showed that folic acid intervention downregulated the upregulation of kidney Nrf2, HO-1, GRP78, and CHOP expression caused by lead exposure. Overall, folic acid alleviates kidney oxidative stress induced by lead exposure by regulating Nrf2 and HO-1, while regulating CHOP and GRP78 to mitigate apoptosis caused by excessive endoplasmic reticulum stress.

Fluoride-Induced Cortical Toxicity in Rats: the Role of Excessive Endoplasmic Reticulum Stress and Its Mediated Defective Autophagy.

The cerebral cortex is closely associated with learning and memory, and fluoride is capable of inducing cortical toxicity, but its mechanism is unclear. This study aimed to investigate the role of endoplasmic reticulum stress and autophagy in fluoride-induced cortical toxicity. Rats exposed to sodium fluoride (NaF) were used as an in vivo model. The results showed that NaF exposure impaired the learning and memory capacities and increased urinary fluoride levels in rats. In addition, NaF exposure induced excessive endoplasmic reticulum stress and associated apoptosis, as evidenced by elevated IRE1α, GRP78, cleaved caspase-12, and cleaved caspase-3, as well as defective autophagy, as evidenced by increased expression of Beclin1, LC3-II, and p62 in cortical areas. Importantly, the endoplasmic reticulum stress inhibitor 4-phenylbutyric acid (4-PBA) alleviated endoplasmic reticulum stress as well as defective autophagy, thus confirming the critical role of endoplasmic reticulum stress and autophagy in fluoride-induced cortical toxicity. Taken together, these results suggest that excessive endoplasmic reticulum stress and its mediated defective autophagy lead to fluoride-induced cortical toxicity. This provides new insights into the mechanisms of fluoride-induced neurotoxicity and a new theoretical basis for the prevention and treatment of fluoride-induced neurotoxicity.

A systems biological analysis of the ATF4-GADD34-CHOP regulatory triangle upon endoplasmic reticulum stress.

Endoplasmic reticulum (ER) stress-dependent accumulation of incorrectly folded proteins leads to activation of the unfolded protein response. The role of the unfolded protein response (UPR) is to avoid cell damage and restore the homeostatic state by autophagy; however, excessive ER stress results in apoptosis. Here we investigated the ER stress-dependent feedback loops inside one of the UPR branches by focusing on PERK-induced ATF4 and its two targets, called CHOP and GADD34. Our goal was to qualitatively describe the dynamic behavior of the system by exploring the key regulatory motifs using both molecular and theoretical biological techniques. Using the HEK293T cell line as a model system, we confirmed that the life-or-death decision is strictly regulated. We investigated the dynamic characteristics of the crucial elements of the PERK pathway at both the RNA and protein level upon tolerable and excessive levels of ER stress. Of particular note, inhibition of GADD34 or CHOP resulted in various phenotypes upon high levels of ER stress. Our computer simulations suggest the existence of two new feedback loops inside the UPR. First, GADD34 seems to have a positive effect on ATF4 activity, while CHOP inhibits it. We claim that these newly described feedback loops ensure the fine-tuning of the ATF4-dependent stress response mechanism of the cell.

Elaiophylin triggers paraptosis and preferentially kills ovarian cancer drug-resistant cells by inducing MAPK hyperactivation

Finely tuned mitogen-activated protein kinase (MAPK) signaling is important for cancer cell survival. Perturbations that push cells out of the MAPK fitness zone result in cell death. Previously, in a screen of the North China Pharmaceutical Group Corporation’s pure compound library of microbial origin, we identified elaiophylin as an autophagy inhibitor. Here, we demonstrated a new role for elaiophylin in inducing excessive endoplasmic reticulum (ER) stress, ER-derived cytoplasmic vacuolization, and consequent paraptosis by hyperactivating the MAPK pathway in multiple cancer cells. Genome-wide CRISPR/Cas9 knockout library screening identified SHP2, an upstream intermediary of the MAPK pathway, as a critical target in elaiophylin-induced paraptosis. The cellular thermal shift assay (CETSA) and surface plasmon resonance (SPR) assay further confirmed the direct binding between the SHP2 and elaiophylin. Inhibition of the SHP2/SOS1/MAPK pathway through SHP2 knockdown or pharmacological inhibitors distinctly attenuated elaiophylin-induced paraptosis and autophagy inhibition. Interestingly, elaiophylin markedly increased the already-elevated MAPK levels and preferentially killed drug-resistant cells with enhanced basal MAPK levels. Elaiophylin overcame drug resistance by triggering paraptosis in multiple tumor-bearing mouse models resistant to platinum, taxane, or PARPi, suggesting that elaiophylin might offer a reasonable therapeutic strategy for refractory ovarian cancer.

The Role of Endoplasmic Reticulum Stress in Differentiation of Cells of Mesenchymal Origin.

Endoplasmic reticulum (ER) is a multifunctional membrane-enclosed organelle. One of the major ER functions is cotranslational transport and processing of secretory, lysosomal, and transmembrane proteins. Impaired protein processing caused by disturbances in the ER homeostasis results in the ER stress. Restoration of normal ER functioning requires activation of an adaptive mechanism involving cell response to misfolded proteins, the so-called unfolded protein response (UPR). Besides controlling protein folding, UPR plays a key role in other physiological processes, in particular, differentiation of cells of connective, muscle, epithelial, and neural tissues. Cell differentiation is induced by the physiological levels of ER stress, while excessive ER stress suppresses differentiation and can result in cell death. So far, it remains unknown whether UPR activation induces cell differentiation or if UPR is initiated by the upregulated synthesis of secretory proteins during cell differentiation. Cell differentiation is an important stage in the development of multicellular organisms and is tightly controlled. Suppression or excessive activation of this process can lead to the development of various pathologies in an organism. In particular, impairments in the differentiation of connective tissue cells can result in the development of fibrosis, obesity, and osteoporosis. Recently, special attention has been paid to fibrosis as one of the major complications of COVID-19. Therefore, studying the role of UPR in the activation of cell differentiation is of both theoretical and practical interest, as it might result in the identification of molecular targets for selective regulation of cell differentiation stages and as well as the potential to modulate the mechanisms involved in the development of various pathological states.

Curcumin Inhibits Hyperandrogen-Induced IRE1α-XBP1 Pathway Activation by Activating the PI3K/AKT Signaling in Ovarian Granulosa Cells of PCOS Model Rats.

Background Hyperandrogenism is a common characteristic of polycystic ovary syndrome (PCOS). Long-term, continuous exposure to hyperandrogenic environments may cause excessive endoplasmic reticulum (ER) stress in ovarian granulosa cells (GCs). Curcumin is a polyphenol extracted from turmeric rhizomes which has several pharmacological effects that may benefit patients with PCOS. To explore whether curcumin can inhibit hyperandrogen-induced ER stress in ovarian GCs of PCOS rats and to elucidate the possible underlying mechanisms. Methods We developed PCOS model rats by exposure to hyperandrogenic conditions and divided the rats into control, PCOS, and PCOS+curcumin (200 mg/kg, for 8 weeks) groups. The levels of ER stress-related proteins and PI3K/AKT phosphorylation were measured in the ovarian tissue of all experimental groups by real-time quantitative PCR, western blotting, immunohistochemistry, and immunofluorescence. Subsequent in vitro analysis on primary cultured GCs was performed to confirm the influence of curcumin on ER stress inhibition by immunofluorescence and western blotting. Results Curcumin protects GCs from hyperandrogen-induced apoptosis in PCOS model rats by inhibiting the ER stress-related IRE1α-XBP1 pathway and activating the PI3K/AKT signaling pathway. Conclusions These observations indicate that curcumin might be a safe and useful supplement for PCOS patients.

CdTe quantum dots trigger oxidative stress and endoplasmic reticulum stress-induced apoptosis and autophagy in rat Schwann cell line RSC96.

In the current study, the cytotoxicity and mechanisms of cadmium telluride quantum dots (CdTe QDs) on RSC96 cells were evaluated by exposing different doses of CdTe QDs for 24 h. Two types of cell death, including apoptosis and autophagy, as well as two important organelles, mitochondria and endoplasmic reticulum, were focused after CdTe QDs exposure. The results showed that CdTe QDs induced apoptosis in RSC96 cells in a concentration-dependent manner; promoted the accumulation of intracellular reactive oxygen species; decreased the mitochondrial membrane potential; caused the release of cytochrome c; and also increased the expression of Bcl-2 associated X protein, caspase-3, and cytochrome c proteins and decreased the expression of Bcl-2 protein. Further results also confirmed that CdTe QDs could be internalized by RSC96 cells, and the exposure and internalization of CdTe QDs could induce excessive endoplasmic reticulum stress in the cells, and the expression levels of binding immunoglobulin protein, C/EBP homologous protein, and caspase12 proteins were increased in a concentration-dependent manner. Moreover, autophagy-related proteins LC3II, Beclin1, and P62 all increased after CdTe QDs exposure, suggesting that CdTe QDs exposure both promoted autophagosome formation and inhibited autophagosome degradation, and that CdTe QDs affected the autophagic flow in RSC96 cells. In conclusion, CdTe QDs are able to cause apoptosis and autophagy in RSC96 cells through mitochondrial and endoplasmic reticulum stress pathways, and the possible neurotoxicity of CdTe QDs should be further investigated.

Effects and molecular mechanism of exogenous L-carnitine on excessive endoplasmic reticulum stress-mediated hepatic pyroptosis in severely scald rats

Effects and molecular mechanism of exogenous L-carnitine on excessive endoplasmic reticulum stress-mediated hepatic pyroptosis in severely scald rats

Rationally Designed Heptamethine Cyanine Photosensitizers that Amplify Tumor-Specific Endoplasmic Reticulum Stress and Boost Antitumor Immunity.

Cancer phototherapy activates immunogenic cell death (ICD) and elicits a systemic antitumor immune response, which is an emerging approach for tumor treatment. Most available photosensitizers require a combination of immune adjuvants or checkpoint inhibitors to trigger antitumor immunity because of the immunosuppressive tumor microenvironment and the limited phototherapeutic effect. A class of tumor-targeting heptamethine cyanine photosensitizers modified with an endoplasmic reticulum (ER)-targeting group (benzenesulfonamide) are synthesized. Phototherapy of tumor cells markedly amplifies ER stress and promotes tumor antigen release, as the ER is required for protein synthesis, secretion, and transport. More importantly, different electron-donating or -withdrawing substitutions are introduced into benzenesulfonamide to modulate the nonradiative decay pathways through intramolecular charge transfer, including singlet-triplet intersystem crossing (photodynamic effect) and internal thermal conversion (photothermal effect). Thus, a heptamethine cyanine photosensitizer containing a binitro-substituted benzenesulfonamide (ER-Cy-poNO2 ) is identified that preferentially accumulates in the ER of tumor cells. It significantly enhances the phototherapeutic effect by inducing excessive ER stress and robust ICD. Consequently, this small molecular photosensitizer triggers a sufficient antitumor immune response and effectively suppresses the growth of both primary and distant metastatic tumors, whereas no apparent toxicity is observed. This heptamethine cyanine photosensitizer has the potential to enhance cancer-targeted immunotherapy.

Coenzyme Q10 attenuates renal fibrosis by inhibiting RIP1-RIP3-MLKL-mediated necroinflammation via Wnt3α/β-catenin/GSK-3β signaling in unilateral ureteral obstruction

ObjectiveCoenzyme Q10 (CoQ10) protects against various types of injury, but its role in preventing renal scarring in chronic kidney disease remains an open question. Herein, we evaluated whether CoQ10 attenuates renal fibrosis by interfering with necroinflammation in a rat model of unilateral ureteral obstruction (UUO) and in vitro. MethodsRats with UUO were treated daily with CoQ10 or an RIP inhibitor (necrostatin-1 or GSK872) for 7 days. The influence of CoQ10 on renal injury caused by UUO was evaluated by histopathology and analysis of gene expression, oxidative stress, intracellular organelles, apoptosis, and Wnt3α/β-catenin/GSK-3β signaling·H2O2-exposed human kidney (HK-2) cells were also examined after treatment with CoQ10 or an RIP inhibitor. ResultsUUO induced marked renal tubular necrosis, upregulation of RIP1-RIP3-MLKL axis proteins, activation of the NLRP3 inflammasome, and evolution of renal fibrosis. UUO-induced oxidative stress evoked excessive endoplasmic reticulum stress and mitochondrial dysfunction, which triggered apoptotic cell death through Wnt3α/β-catenin/GSK-3β signaling. All of these effects were mitigated by CoQ10 or an RIP inhibitor. In H2O2-treated HK-2 cells, CoQ10 or an RIP inhibitor suppressed the expression of RIP1-RIP3-MLKL proteins and pyroptosis-related cytokines, and hindered the production of intracellular reactive oxygen species as shown by MitoSOX Red staining and apoptotic cell death but increased cell viability. The CoQ10 or Wnt/β-catenin inhibitor ICG-001 deactivated H2O2-stimulated activation of Wnt3α/β-catenin/GSK-3β signaling. ConclusionThese findings suggest that CoQ10 attenuates renal fibrosis by inhibiting RIP1-RIP3-MLKL-mediated necroinflammation via Wnt3α/β-catenin/GSK-3β signaling in UUO.

Molecular and functional characterization of the retinol-binding protein 4 (RBP4) in hepatocytes of Schizothorax prenanti in response to palmitic acid.

Retinol-binding protein 4 (RBP4) protein is a kind of adipokines synthesized and secreted by the liver, which has been verified to play important roles in liver metabolism and energy homeostasis. However, the effects of RBP4 on hepatic lipid accumulation are still elusive in fish. In the present study, we cloned and characterized the RBP4 gene in Schizothorax prenanti (S. prenanti). RBP4 gene was specifically expressed in the liver and abdominal adipose tissue. Palmitic acid (PA; 400μM) can significantly increase lipid deposition in primary hepatocytes after 12h of treatment. Furthermore, RBP4 knockdown can relieve the excessive lipid deposition and endoplasmic reticulum stress in the hepatocytes caused by PA. The inhibition of RBP4 abolished the ability of PA to induce the expression of genes involved in lipogenesis and endoplasmic reticulum stress. These results demonstrate that RBP4 inhibition attenuated PA-induced lipid deposition and endoplasmic reticulum stress in hepatocytes of S. prenanti. This study could contribute to improve the understanding of RBP4 functions in the PA-induced lipid deposition in hepatocytes of fish.

Integrated chemical profiling, network pharmacology and pharmacological evaluation to explore the potential mechanism of Xinbao pill against myocardial ischaemia–reperfusion injury

Context Xinbao pill (XBW), a traditional Chinese herbal formula, is widely used in clinical treatment for cardiovascular diseases; however, the therapeutic effect of XBW on myocardial ischaemia–reperfusion injury (MI/RI) is unclear. Objective This study evaluates the cardioprotective effect and molecular mechanism of XBW against MI/RI. Materials and methods A phytochemistry-based network pharmacology analysis was used to uncover the mechanism of XBW against MI/RI. Ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method was used to identify chemicals. MI/RI-related targets of XBW were predicted using TargetNet database, OMIC database, etc. Sprague-Dawley (SD) rats under anterior descending artery ligation model were divided into Sham, MI/RI and XBW (180 mg/kg, intragastric administration). After 30 min ischaemia and 24 h reperfusion, heart tissues were collected for measurement of myocardial infarct size. After oxygen glucose deprivation for 6 h, H9c2 cells were treated with XBW (60, 240 and 720 μg/mL) and diazoxide (100 μM) for 18 h of reperfusion. Results Thirty-seven chemicals were identified in XBW; 50 MI/RI-related targets of XBW were predicted using indicated databases. XBW significantly reduced infarct size and creatine kinase MB (CK-MB) level after MI/RI; XBW protected H9c2 cells against OGD/R injury. Gene ontology (GO) and KEGG pathway enrichment analyses by String database showed that the cardioprotective effect of XBW was associated with autophagy and apoptosis signalling pathways. Experimental investigation also verified that XBW suppressed apoptosis, autophagy and endoplasmic reticulum (ER) stress. Conclusions XBW showed therapeutic effects against MI/RI mainly via attenuating apoptosis though suppressing excessive autophagy and ER stress.

Molecular origin of somatostatin-positive neuron vulnerability.

Reduced somatostatin (SST) and dysfunction of SST-positive (SST+) neurons are hallmarks of neurological disorders and associated with mood disturbances, but the molecular origin of SST+ neuron vulnerability is unknown. Using chronic psychosocial stress as a paradigm to induce elevated behavioral emotionality in rodents, we report a selective vulnerability of SST+ neurons through exacerbated unfolded protein response (UPR) of the endoplasmic reticulum (ER), or ER stress, in the prefrontal cortex. We next show that genetically suppressing ER stress in SST+ neurons, but not in pyramidal neurons, normalized behavioral emotionality induced by psychosocial stress. In search for intrinsic factors mediating SST+ neuron vulnerability, we found that the forced expression of the SST precursor protein (preproSST) in SST+ neurons, mimicking psychosocial stress-induced early proteomic changes, induces ER stress, whereas mature SST or processing-incompetent preproSST does not. Biochemical analyses further show that psychosocial stress induces SST protein aggregation under elevated ER stress conditions. These results demonstrate that SST processing in the ER is a SST+ neuron-intrinsic vulnerability factor under conditions of sustained or over-activated UPR, hence negatively impacting SST+ neuron functions. Combined with observations in major medical illness, such as diabetes, where excess ER processing of preproinsulin similarly causes ER stress and β cell dysfunction, this suggests a universal mechanism for proteinopathy that is induced by excess processing of native endogenous proteins, playing critical pathophysiological roles that extend to neuropsychiatric disorders.

Jianpi Qingchang Decoction Ameliorates Chronic Colitis in Piroxicam-Induced IL-10 Knockout Mice by Inhibiting Endoplasmic Reticulum Stress.

Background Excessive endoplasmic reticulum (ER) stress in intestinal epithelial cells (IEC) may lead to impaired intestinal mucosal barrier function and then participate in the pathogenesis of ulcerative colitis (UC). Jianpi Qingchang decoction (JPQCD) has been shown to have protective effects on UC. However, further studies are needed to determine whether JPQCD regulates PERK/eIF2α/ATF4/CHOP pathways to play a role in treating UC. Methods IL-10 −/− mice were randomly assigned into five groups: control, model, low-dose JPQCD (JPQCD L), middle-dose JPQCD (JPQCD M), and high-dose JPQCD (JPQCD H). All groups except for the control group were given model feed containing 200 ppm piroxicam for 10 d to induce colitis. As a comparison, we used wild-type mice that were the progeny of IL-10+/− matings, bred in the same facility. The control group and wild-type mice were fed with common feed. At the same time, mice in each group were given corresponding drugs by gavage for 14 d. The disease activity index of mice in each group was evaluated daily. Colon tissues of mice were collected, colon length was measured, and pathological changes and ultrastructure of colon epithelial cells were observed. The effects of JPQCD on the PERK/eIF2α/ATF4/CHOP pathways were evaluated by western blotting and reverse transcription-polymerase chain reaction (RT-PCR). The expression of CHOP in colon tissue was detected by tissue immunofluorescence assay. The expression of NF-κB, p-NF-κB p65 protein was analyzed by western blotting; the level of IL-17 in colon tissue was detected by enzyme-linked immunosorbent assay (ELISA) and verified by examining NF-κB and IL-17 mRNA levels by RT-PCR. Results Compared with the control group, the model group showed significant colitis symptoms and severe colonic tissue damage. The results showed that JPQCD significantly reduced body weight loss, ameliorated disease activity index, and restored colon length in IL-10−/− mice with piroxicam-induced colitis. Western blotting and RT-PCR showed that the PERK/eIF2α/ATF4/CHOP pathway was activated in colon tissue of model mice, suggesting that the pathway is involved in the pathogenesis of ulcerative colitis (UC) and could become a potential therapeutic target. The JPQCD treatment inhibited the activation of the PERK/eIF2α/ATF4/CHOP pathway, alleviated the ER stress, and played a role in preventing and treating UC. In addition, JPQCD can also downregulate the protein of NF-κB, p-NF-κB p65, downregulate the mRNA expression of NF-κB, and reduce the content of IL-17 and its mRNA expression in colon tissues. Conclusion JPQCD may play a protective role in UC by regulating the PERK/eIF2α/ATF4/CHOP signaling pathway and relieving endoplasmic reticulum stress.

Selenoprotein K protects skeletal muscle from damage and is required for satellite cells-mediated myogenic differentiation

The regeneration of adult skeletal muscle after injury is primarily initiated by satellite cells (SCs), but the regulatory mechanisms of cells committed to myogenic differentiation remain poorly explored. Small molecular selenoprotein K (SelK) plays crucial roles in the modulation of endoplasmic reticulum (ER) stress and against oxidative stress. Here, we first showed that SelK expression is activated in myogenic cells during differentiation both in vivo and in vitro. Meanwhile, loss of SelK delayed skeletal muscle regeneration, inhibited the development of myoblasts into myotubes, and was accompanied by reduced expression of myogenic regulatory factors (MRFs). Moreover, ER stress, intracellular reactive oxygen species (ROS), autophagy and apoptosis under myogenesis induction were more severe in SelK-deficient mice and cells than in the corresponding control groups. Supplementation with specific inhibitors to alleviate excessive ER stress or oxidative stress partly rescued the differentiation potential and formation of myotubes. Notably, we demonstrated that Self-mediated regulation of cellular redox status was primarily derived from its subsequent effects on ER stress. Together, our results suggest that SelK protects skeletal muscle from damage and is a crucial regulator of myogenesis.

MFG-E8 Maintains Cellular Homeostasis by Suppressing Endoplasmic Reticulum Stress in Pancreatic Exocrine Acinar Cells.

Excessive endoplasmic reticulum (ER) stress contributes significantly to the pathogenesis of exocrine acinar damage in acute pancreatitis. Our previous study found that milk fat globule EGF factor 8 (MFG-E8), a lipophilic glycoprotein, alleviates acinar cell damage during AP via binding to αvβ3/5 integrins. Ligand-dependent integrin-FAK activation of STAT3 was reported to be of great importance for maintaining cellular homeostasis. However, MFG-E8’s role in ER stress in pancreatic exocrine acinar cells has not been evaluated. To study this, thapsigargin, brefeldin A, tunicamycin and cerulein + LPS were used to induce ER stress in rat pancreatic acinar cells in vitro. L-arginine- and cerulein + LPS-induced acute pancreatitis in mice were used to study ER stress in vivo. The results showed that MFG-E8 dose-dependently inhibited ER stress under both in vitro and in vivo conditions. MFG-E8 knockout mice suffered more severe ER stress and greater inflammatory response after L-arginine administration. Mechanistically, MFG-E8 increased phosphorylation of FAK and STAT3 in cerulein + LPS-treated pancreatic acinar cells. The presence of specific inhibitors of αvβ3/5 integrin, FAK or STAT3 abolished MFG-E8’s effect on cerulein + LPS-induced ER stress in pancreatic acinar cells. In conclusion, MFG-E8 maintains cellular homeostasis by alleviating ER stress in pancreatic exocrine acinar cells.

Salubrinal alleviates traumatic spinal cord injury through suppression of the eIF2α/ATF4 pathway in mouse model

Spinal cord injury (SCI) remains an intractable clinical challenge of neurosurgery, it can be divided into two stages: uncontrollable primary injury induced by mechanical damage and controllable secondary injury regulated by continuous cell death. The apoptosis was the one of most important events in secondary injury, previous studies revealed that excessive endoplasmic reticulum (ER) stress breaks down the homeostasis and triggers apoptosis in the spinal cord. To deter or alleviate the secondary jury, we screen one of fat-soluble compounds, salubrinal, which was an inhibitor of eIF2α dephosphorylation can repair SCI by inhibiting ER stress in mice after SCI. Administration of salubrinal effectively represses apoptosis, protects neuronal cell, and promotes the restoration of locomotor function in mice SCI models. Furthermore, the level of phosphorylated eIF2α was raised in the presence of salubrinal, but the protein expression of ATF4 and CHOP was downregulated. Unexpectedly, transcriptional expression of CHOP-regulated pro-apoptotic genes was decreased. These data suggest salubrinal suppress ER stress by targeting eIF2α/ATF4 pathways and reduces cell death after SCI. It is suggested that the mitigation of secondary lesion by inhibiting ER stress induced apoptosis in the early phase of SCI is promising treatment strategy.

A marine-derived small molecule induces immunogenic cell death against triple-negative breast cancer through ER stress-CHOP pathway.

Although triple-negative breast cancer (TNBC) is the most refractory subtype among all breast cancers, it has been shown to have higher immune infiltration than other subtypes. We identified the marine-derived small molecule MHO7, which acts as a potent immunogenic cell death (ICD) inducer through the endoplasmic reticulum (ER) stress-C/EBP-homologous protein (CHOP) pathway, to treat TNBC. MHO7 exerted cytostatic and cytotoxic effects on TNBC cells at an IC50 of 0.96-1.75 µM and suppressed tumor growth with an approximately 80% inhibition rate at a dose of 60 mg/kg. In 4T1 cell tumor-bearing mice, 30 mg/kg MHO7 inhibited pulmonary metastasis with an efficacy of 70.26%. Transcriptome analyses revealed that MHO7 changed the transcription of genes related to ribosome and protein processes in the ER. MHO7 also triggered reactive oxygen species (ROS) generation and attenuated glutathione (GSH) levels, which caused excessive oxidative stress and ER stress via the PERK/eIF2α/AFT4/CHOP pathway and led to cell apoptosis. ER stress and ROS production facilitated the release of ICD-related danger-associated molecular patterns (DAMPs) from TNBC cells, which activated the immune response in vivo, as indicated by the release of antitumor cytokines such as IL-6, IL-1β, IFN-γ, and TNF-α, increases in CD86+ and MHC-II dendritic cells and CD4+ and CD8+ T cells and a decrease in regulatory T cells (Tregs). These results reveal that MHO7 triggers an aggressive stress response to amplify tumor immunogenicity and induce a robust immune response. This synergistic effect inhibits primary breast cancer growth and spontaneous metastasis in TNBC, providing a new strategy for TNBC treatment.

Cell cycle regulation of ER membrane biogenesis protects against chromosome missegregation.

Failure to reorganize the endoplasmic reticulum (ER) in mitosis results in chromosome missegregation. Here, we show that accurate chromosome segregation in human cells requires cell cycle-regulated ER membrane production. Excess ER membranes increase the viscosity of the mitotic cytoplasm to physically restrict chromosome movements, which impedes the correction of mitotic errors leading to the formation of micronuclei. Mechanistically, we demonstrate that the protein phosphatase CTDNEP1 counteracts mTOR kinase to establish a dephosphorylated pool of the phosphatidic acid phosphatase lipin 1 in interphase. CTDNEP1 control of lipin 1 limits the synthesis of fatty acids for ER membrane biogenesis in interphase that then protects against chromosome missegregation in mitosis. Thus, regulation of ER size can dictate the biophysical properties of mitotic cells, providing an explanation for why ER reorganization is necessary for mitotic fidelity. Our data further suggest that dysregulated lipid metabolism is a potential source of aneuploidy in cancer cells.