OBJECTIVE: To investigate the effects of astragaloside IV (AS-IV) on podocyte injury of diabetic nephropathy (DN) and reveal its potential mechanism. METHODS: In in vitro experiment, podocytes were divided into 4 groups, normal, high glucose (HG), inositol-requiring enzyme 1 (IRE-1) α activator (HG+thapsigargin 1 µmol/L), and IRE-1α inhibitor (HG+STF-083010, 20 µmol/L) groups. Additionally, podocytes were divided into 4 groups, including normal, HG, AS-IV (HG+AS-IV 20 µmol/L), and IRE-1α inhibitor (HG+STF-083010, 20 µmol/L) groups, respectively. After 24 h treatment, the morphology of podocytes and endoplasmic reticulum (ER) was observed by electron microscopy. The expressions of glucose-regulated protein 78 (GRP78) and IRE-1α were detected by cellular immunofluorescence. In in vivo experiment, DN rat model was established via a consecutive 3-day intraperitoneal streptozotocin (STZ) injections. A total of 40 rats were assigned into the normal, DN, AS-IV [AS-IV 40 mg/(kg·d)], and IRE-1α inhibitor [STF-083010, 10 mg/(kg·d)] groups (n=10), respectively. The general condition, 24-h urine volume, random blood glucose, urinary protein excretion rate (UAER), urea nitrogen (BUN), and serum creatinine (SCr) levels of rats were measured after 8 weeks of intervention. Pathological changes in the renal tissue were observed by hematoxylin and eosin (HE) staining. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were used to detect the expressions of GRP78, IRE-1α, nuclear factor kappa Bp65 (NF-κBp65), interleukin (IL)-1β, NLR family pyrin domain containing 3 (NLRP3), caspase-1, gasdermin D-N (GSDMD-N), and nephrin at the mRNA and protein levels in vivo and in vitro, respectively. RESULTS: Cytoplasmic vacuolation and ER swelling were observed in the HG and IRE-1α activator groups. Podocyte morphology and ER expansion were improved in AS-IV and IRE-1α inhibitor groups compared with HG group. Cellular immunofluorescence showed that compared with the normal group, the fluorescence intensity of GRP78 and IRE-1α in the HG and IRE-1α activator groups were significantly increased whereas decreased in AS-IV and IRE-1α inhibitor groups (P<0.05). Compared with the normal group, the mRNA and protein expressions of GRP78, IRE-1α, NF-κ Bp65, IL-1β, NLRP3, caspase-1 and GSDMD-N in the HG group was increased (P<0.05). Compared with HG group, the expression of above indices was decreased in the AS-IV and IRE-1α inhibitor groups, and the expression in the IRE-1α activator group was increased (P<0.05). The expression of nephrin was decreased in the HG group, and increased in AS-IV and IRE-1α inhibitor groups (P<0.05). The in vivo experiment results revealed that compared to the normal group, the levels of blood glucose, triglyceride, total cholesterol, BUN, blood creatinine and urinary protein in the DN group were higher (P<0.05). Compared with DN group, the above indices in AS-IV and IRE-1α inhibitor groups were decreased (P<0.05). HE staining revealed glomerular hypertrophy, mesangial widening and mesangial cell proliferation in the renal tissue of the DN group. Compared with the DN group, the above pathological changes in renal tissue of AS-IV and IRE-1α inhibitor groups were alleviated. Quantitative RT-PCR and Western blot results of GRP78, IRE-1α, NF-κ Bp65, IL-1β, NLRP3, caspase-1 and GSDMD-N were consistent with immunofluorescence analysis. CONCLUSION AS-IV could reduce ERS and inflammation, improve podocyte pyroptosis, thus exerting a podocyte-protective effect in DN, through regulating IRE-1α/NF-κ B/NLRP3 signaling pathway.
Podocytes/metabolism* ; Animals ; Diabetic Nephropathies/metabolism* ; Saponins/therapeutic use* ; Triterpenes/therapeutic use* ; Signal Transduction/drug effects* ; NF-kappa B/metabolism* ; Protein Serine-Threonine Kinases/metabolism* ; Male ; Rats, Sprague-Dawley ; NLR Family, Pyrin Domain-Containing 3 Protein/metabolism* ; Endoribonucleases/metabolism* ; Endoplasmic Reticulum Chaperone BiP ; Rats ; Diabetes Mellitus, Experimental/complications* ; Endoplasmic Reticulum/metabolism* ; Multienzyme Complexes

OBJECTIVE: To explore the mechanism of crocin, a major active component of Crocus sativus (Zanghonghua), in regulating amyloid beta (Aβ) generation, endoplasmic reticulum (ER) stress, and autophagy in neuronal cells, with potential therapeutic applications in Alzheimer's disease (AD). METHODS: Mouse neuroblastoma Neuron2a (N2a) cells stably transfected with the human amyloid precursor protein (APP) Swedish mutant was used as a cellular model for AD (N2a/APP). Control cells were vector transfected (N2a/vector). The effects of 3 different doses of crocin on reactive oxygen species (ROS) generation, cytosolic calcium, and apoptosis were evaluated by flow cytometry. Aβ levels were determined by enzyme-linked immunosorbent assay. APP processing and ER stress proteins expressions were determined by Western blot. Autophagosome formation was evaluated by autophagy detection kit and confocal microscope. RESULTS: Crocin inhibited APP expression in N2a/APP cells and promoted α-cleavage of APP processing, while modestly reduced beta-secretase 1 (BACE1) and presenilin 1 (PS1, P<0.05 or P<0.01). ER stress markers, including the binding immunoglobulin protein/78-kD glucose-regulated protein (Bip/GRP78) and C/EBP homologous protein (CHOP), were elevated in N2a/APP cells compared to N2a/vector cells (P<0.05). Crocin could effectively reduce the levels of ER stress (P<0.05 or P<0.01). In addition, crocin enhanced autophagy by promoting formation of autophagosome (P<0.05 or P<0.01). CONCLUSION Crocin significantly inhibited Aβ generation by promoting α-cleavage of APP processing, inhibiting ER stress-associated unfolded protein response, and regulating autophagy.
Endoplasmic Reticulum Stress/drug effects* ; Autophagy/drug effects* ; Animals ; Endoplasmic Reticulum Chaperone BiP ; Mice ; Amyloid beta-Peptides/metabolism* ; Amyloid beta-Protein Precursor/metabolism* ; Carotenoids/pharmacology* ; Humans ; Cell Line, Tumor ; Reactive Oxygen Species/metabolism* ; Apoptosis/drug effects* ; Calcium/metabolism*

OBJECTIVES: The integrated endoplasmic reticulum stress inhibitor (ISRIB) is a selective inhibitor of the protein kinase R-like endoplasmic reticulum kinase (PERK) signaling pathway within endoplasmic reticulum stress (ERS) and can improve spatial and working memory in aged mice. Although ERS and oxidative stress are tightly interconnected, it remains unclear whether ISRIB alleviates cognitive impairment by restoring the balance between ERS and oxidative stress. This study aims to investigate the effects and mechanisms of ISRIB on lipopolysaccharide (LPS)-induced cognitive impairment in mice. METHODS: Eight-week-old male ICR mice were randomly divided into 3 groups: Normal saline (NS) group, LPS group, and ISRIB+LPS group. NS and LPS groups received daily intraperitoneal injections of normal saline for 7 days; on day 7, LPS group mice received intraperitoneal LPS (0.83 mg/kg) to establish a cognitive impairment model. ISRIB+LPS group received ISRIB (0.25 mg/kg) intraperitoneally for 7 days, with LPS injected 30 minutes after ISRIB on day 7. Cognitive ability was evaluated by the novel place recognition test (NPRT). Real-time fluorogenic quantitative PCR (RT-qPCR) was used to detect changes in nitric oxide synthase (NOS), superoxide dismutase-1 (SOD-1), and catalase (CAT) gene expression in the hippocampus and prefrontal cortex. Oxidative stress markers malondialdehyde (MDA), glutathione (GSH), and oxidized glutathione (GSSG), were measured in hippocampal and prefrontal cortex tissues. RESULTS: Compared with the NS group, mice in LPS group showed a significant reduction in novel place recognition ratio, upregulation of hippocampal NOS-1 and NOS-2 mRNA, downregulation of SOD-1 and CAT mRNA, increased MDA and GSSG, decreased GSH, and reduced GSH/GSSG ratio (all P<0.05). Compared with the LPS group, mice in ISRIB+LPS group exhibited significantly improved novel place recognition, downregulated NOS-1 and NOS-2 mRNA, upregulated SOD-1 and CAT mRNA, decreased MDA and GSSG, increased GSH, and an elevated GSH/GSSG ratio in the hippocampus (all P<0.05). No significant changes were observed in the prefrontal cortex. CONCLUSIONS ISRIB improves LPS-induced cognitive impairment in mice by restoring the oxidative/antioxidant balance in the hippocampus.
Animals ; Lipopolysaccharides ; Male ; Mice, Inbred ICR ; Cognitive Dysfunction/drug therapy* ; Mice ; Oxidative Stress/drug effects* ; Endoplasmic Reticulum Stress/drug effects* ; Hippocampus/drug effects* ; Nitric Oxide Synthase Type II/genetics* ; Guanidines/pharmacology* ; eIF-2 Kinase/antagonists & inhibitors* ; Signal Transduction/drug effects* ; Superoxide Dismutase/metabolism*

OBJECTIVES: To explore the effects of cannabidiol on endoplasmic reticulum stress and neuronal apoptosis in rats with multiple concussions (MCC). METHODS: SD rats were randomized into sham group, MCC group, 1% tween20 (TW) treatment group, and low-dose (10 mg/kg) and high-dose (40 mg/kg) cannabidiol treatment groups. In all but the sham group, MCC models were established using a metal pendulum percussion device, after which the rats received daily intraperitoneal injections of the corresponding agents for 2 weeks. The expressions of PERK, eIF2α, ATF4, CHOP, TRIB3, p-Akt and pro-caspase-3 in the brain tissue of the rats were detected with qRT-PCR, Western blotting and immunofluorescence staining. The core targets of cannabidiol in treatment of traumatic brain injury (TBI) were identified by network pharmacology analysis, and molecular docking was carried out to simulate the interaction of cannabidiol with the factors related to endoplasmic reticulum stress and apoptosis. RESULTS: Compared with the sham-operated rats, the rat models of MCC showed significantly increased mRNA expressions of PERK, eIF2α and CHOP and protein expressions of PERK, eIF2α, ATF4, CHOP, TRIB3, p-AKT and pro-caspase-3 in the cerebral cortex. CBD treatment, especially at the high dose, obviously increased the expression of p-Akt and lowered the expression levels of the other factors tested in the rat models. Network pharmacology analysis indicated interactions of the core targets of CBD with the factors related to endoplasmic reticulum stress and TBI, and molecular docking study showed a high binding energy of CBD with multiple factors pertaining to endoplasmic reticulum stress and apoptosis. CONCLUSIONS MCC induce endoplasmic reticulum stress and apoptosis in rat brain tissues, for which CBD, especially at a high dose, provides neuroprotective effects by inhibiting endoplasmic reticulum stress and cell apoptosis.
Animals ; Endoplasmic Reticulum Stress/drug effects* ; Apoptosis/drug effects* ; Rats, Sprague-Dawley ; Activating Transcription Factor 4/metabolism* ; Transcription Factor CHOP/metabolism* ; Rats ; Eukaryotic Initiation Factor-2/metabolism* ; Signal Transduction/drug effects* ; eIF-2 Kinase/metabolism* ; Cannabidiol/pharmacology* ; Neurons/metabolism* ; Brain Concussion/metabolism* ; Male ; Molecular Docking Simulation

OBJECTIVES: To examine the changes in serum levels of endoplasmic reticulum stress (ERS) proteins GRP78/CHOP in patients with lupus nephritis (LN) and analyze their diagnostic value and association with renal pathological features. METHODS: From a sample bank established based on a multicenter cohort study of systemic lupus erythematosus (SLE), 60 LN patients and 35 SLE patients without renal involvement were randomly selected. ELISA was used to detect serum levels of GRP78 and CHOP in the patients to analyze their correlation with clinical features and their diagnostic ability for LN and active LN. MRL/lpr mice were used as an animal model of LN to examine their serum levels of GRP78 and CHOP expression and renal expressions of endoplasmic reticulum apoptosis-related proteins. RESULTS: Serum GRP78 and CHOP levels were significantly higher in LN patients than in SLE patients without renal involvement (P<0.05), and were also higher in active LN patients than in patients in the stable phase (P<0.05). Correlation analysis indicated that serum GRP78 and CHOP levels were positively correlated with SLEDAI scores and 24-h urinary protein. ROC analysis showed that CHOP had a high diagnostic ability for LN (AUC=0.762) and active LN (AUC=0.933). Consistent with the clinical findings, serum GRP78 and CHOP levels were elevated in LN mice, and the expressions of PERK and IRE1α pathway proteins were also increased in the kidneys of the mice. TUNEL staining showed increased renal cell apoptosis and elevated renal expressions of apoptosis-related proteins in LN mice. CONCLUSIONS Serum levels of GRP78/CHOP are increased in LN patients possibly in association with ERS-induced apoptosis mediated by the PERK/IRE1α dual pathway.
Endoplasmic Reticulum Chaperone BiP ; Lupus Nephritis/blood* ; Transcription Factor CHOP/blood* ; Heat-Shock Proteins/blood* ; Animals ; Apoptosis ; Humans ; Mice ; Mice, Inbred MRL lpr ; Female ; Adult ; Endoribonucleases/metabolism* ; Male ; eIF-2 Kinase/metabolism* ; Protein Serine-Threonine Kinases/metabolism* ; Young Adult ; Endoplasmic Reticulum Stress ; Kidney/metabolism* ; Middle Aged ; Signal Transduction

Microglial functions are linked to Ca²⁺ signaling, with endoplasmic reticulum (ER) calcium stores playing a crucial role. Microglial abnormality is a hallmark of Alzheimer's disease (AD), but how ER Ca²⁺ receptors regulate microglial functions under physiological and AD conditions remains unclear. We found reduced ryanodine receptor 2 (Ryr2) expression in microglia from an AD mouse model. Modulation of RyR2 using S107, a RyR-Calstabin stabilizer, blunted spontaneous Ca²⁺ transients in controls and normalized Ca²⁺ transients in AD mice. S107 enhanced ATP-induced migration and phagocytosis while reducing ramification in control microglia; however, these effects were absent in AD microglia. Our findings indicate that RyR2 stabilization promotes an activation state shift in control microglia, a mechanism impaired in AD. These results highlight the role of ER Ca²⁺ receptors in both homeostatic and AD microglia, providing insights into microglial Ca²⁺ malfunctions in AD.
Animals ; Microglia/pathology* ; Alzheimer Disease/pathology* ; Phagocytosis/drug effects* ; Ryanodine Receptor Calcium Release Channel/metabolism* ; Disease Models, Animal ; Mice ; Cell Movement/drug effects* ; Mice, Transgenic ; Calcium Signaling/physiology* ; Calcium/metabolism* ; Mice, Inbred C57BL ; Male ; Endoplasmic Reticulum/metabolism*

Pyroptosis is an identified programmed cell death that has been highly linked to endoplasmic reticulum (ER) dynamics. However, the crucial proteins for modulating dynamic ER membrane curvature change that trigger pyroptosis are currently not well understood. In this study, a biotin-labeled chemical probe of potent pyroptosis inducer α-mangostin (α-MG) was synthesized. Through protein microarray analysis, reticulon-4 (RTN4/Nogo), a crucial regulator of ER membrane curvature, was identified as a target of α-MG. We observed that chemically induced proteasome degradation of RTN4 by α-MG through recruiting E3 ligase UBR5 significantly enhances the pyroptosis phenotype in cancer cells. Interestingly, the downregulation of RTN4 expression significantly facilitated a dynamic remodeling of ER membrane curvature through a transition from tubules to sheets, consequently leading to rapid fusion of the ER with the cell plasma membrane. In particular, the ER-to-plasma membrane fusion process is supported by the observed translocation of several crucial ER markers to the "bubble" structures of pyroptotic cells. Furthermore, α-MG-induced RTN4 knockdown leads to pyruvate kinase M2 (PKM2)-dependent conventional caspase-3/gasdermin E (GSDME) cleavages for pyroptosis progression. In vivo, we observed that chemical or genetic RTN4 knockdown significantly inhibited cancer cells growth, which further exhibited an antitumor immune response with anti-programmed death-1 (anti-PD-1). In translational research, RTN4 high expression was closely correlated with the tumor metastasis and death of patients. Taken together, RTN4 plays a fundamental role in inducing pyroptosis through the modulation of ER membrane curvature remodeling, thus representing a prospective druggable target for anticancer immunotherapy.
Pyroptosis/immunology* ; Humans ; Endoplasmic Reticulum/immunology* ; Animals ; Nogo Proteins/antagonists & inhibitors* ; Mice ; Cell Line, Tumor ; Xanthones/pharmacology* ; Neoplasms/pathology* ; Mice, Nude

Diabetic cardiomyopathy (DCM) is a medical condition characterized by cardiac remodeling and dysfunction in individuals with diabetes mellitus. Sarcoplasmic reticulum (SR) and mitochondrial Ca²⁺ overload in cardiomyocytes have been recognized as biological hallmarks in DCM; however, the specific factors underlying these abnormalities remain largely unknown. In this study, we aimed to investigate the role of a cardiac-specific long noncoding RNA, D830005E20Rik (Trdn-as), in DCM. Our results revealed the remarkably upregulation of Trdn-as in the hearts of the DCM mice and cardiomyocytes treated with high glucose (HG). Knocking down Trdn-as in cardiac tissues significantly improved cardiac dysfunction and remodeling in the DCM mice. Conversely, Trdn-as overexpression resulted in cardiac damage resembling that observed in the DCM mice. At the cellular level, Trdn-as induced Ca²⁺ overload in the SR and mitochondria, leading to mitochondrial dysfunction. RNA-seq and bioinformatics analyses identified calsequestrin 2 (Casq2), a primary calcium-binding protein in the junctional SR, as a potential target of Trdn-as. Further investigations revealed that Trdn-as facilitated the recruitment of METTL14 to the Casq2 mRNA, thereby enhancing the m⁶A modification of Casq2. This modification increased the stability of Casq2 mRNA and subsequently led to increased protein expression. When Casq2 was knocked down, the promoting effects of Trdn-as on Ca²⁺ overload and mitochondrial damage were mitigated. These findings provide valuable insights into the pathogenesis of DCM and suggest Trdn-as as a potential therapeutic target for this condition.
Animals ; Diabetic Cardiomyopathies/pathology* ; RNA, Long Noncoding/genetics* ; Myocytes, Cardiac/metabolism* ; Mice ; Calsequestrin/genetics* ; Calcium/metabolism* ; Male ; Sarcoplasmic Reticulum/metabolism* ; Methyltransferases/metabolism* ; Mice, Inbred C57BL ; Mitochondria, Heart/metabolism* ; Disease Models, Animal ; Mitochondria/metabolism*

Activating transcription factor 5 (ATF5) is a member of the activating transcription factor/cyclic adenosine monophosphate response element binding protein (ATF/CREB) family. As a stress-induced transcription factor, ATF5 plays a crucial role in cellular inflammatory stress responses. Under cellular inflammatory stress conditions, ATF5 maintains cell homeostasis and survival by regulating key genes in the mitochondrial unfolded protein response (UPR^mt) and endoplasmic reticulum stress (ERS). As a key regulator in UPR^mt, ATF5 senses mitochondrial stress and translocate to the nucleus to activate the transcription of UPR^mt-related genes, thereby promoting mitochondrial function recovery. Meanwhile, in ERS, ATF5 maintains endoplasmic reticulum homeostasis by regulating the expression of genes related to protein folding, degradation, and apoptosis, determining cell survival or death. ATF5 plays a vital role in various cellular inflammatory stress responses. In infectious inflammation, ATF5 plays an important role in alleviating neuroinflammation and maintaining intestinal barrier function by regulating UPR^mt. In inflammation related to degenerative diseases, ATF5 improves intervertebral disc degeneration and delays the progression of osteoarthritis by regulating UPR^mt. In metabolic inflammation such as diabetes and obesity, ATF5 regulates UPR^mt and ERS to maintain the function of pancreatic β-cells, controlling their survival or inducing apoptosis, thus influencing the progression of diabetes. ATF5 protects mitochondria in the kidneys, adipose tissue, and pancreas, slows the progression of diabetic nephropathy, and improves insulin sensitivity. Furthermore, in immune-related inflammation, ATF5 alleviates glomerulonephritis and promotes tissue repair by enhancing immune tolerance in dendritic cells. In summary, ATF5, as a key regulator in cellular inflammatory stress responses, maintains cell homeostasis through regulating UPR^mt and ERS and determines cell fate. Its critical regulatory role in cellular inflammatory stress responses makes ATF5 a potential clinical therapeutic target. This article summarizes the structural features and translational regulatory mechanisms of ATF5, focusing on its role in cellular inflammatory stress responses, particularly its regulatory mechanisms in UPR^mt and ERS, aiming to provide a theoretical basis for understanding ATF5's role in cell and organ protection and to offer new insights into the treatment of related inflammatory diseases.
Humans ; Endoplasmic Reticulum Stress ; Inflammation/metabolism* ; Activating Transcription Factors/metabolism* ; Unfolded Protein Response ; Mitochondria/metabolism* ; Apoptosis ; Animals

Magnolol, a compound extracted from Magnolia officinalis, demonstrates potential efficacy in addressing metabolic dysfunction and cardiovascular diseases. Its biological activities encompass anti-inflammatory, antioxidant, anticoagulant, and anti-diabetic effects. Growth/differentiation factor-15 (GDF-15), a member of the transforming growth factor β superfamily, is considered a potential therapeutic target for metabolic disorders. This study investigated the impact of magnolol on GDF-15 production and its underlying mechanism. The research examined the pharmacological effect of magnolol on GDF-15 expression in vitro and in vivo, and determined the involvement of endoplasmic reticulum (ER) stress signaling in this process. Luciferase reporter assays, chromatin immunoprecipitation, and in vitro DNA binding assays were employed to examine the regulation of GDF-15 by activating transcription factor 4 (ATF4), CCAAT enhancer binding protein γ (CEBPG), and CCCTC-binding factor (CTCF). The study also investigated the effect of magnolol and ATF4 on the activity of a putative enhancer located in the intron of the GDF-15 gene, as well as the influence of single nucleotide polymorphisms (SNPs) on magnolol and ATF4-induced transcription activity. Results demonstrated that magnolol triggers GDF-15 production in endothelial cells (ECs), hepatoma cell line G2 (HepG2) and hepatoma cell line 3B (Hep3B) cell lines, and primary mouse hepatocytes. The cooperative binding of ATF4 and CEBPG upstream of the GDF-15 gene or the E1944285 enhancer located in the intron led to full-power transcription of the GDF-15 gene. SNP alleles were found to impact the magnolol and ATF4-induced transcription activity of GDF-15. In high-fat diet ApoE^-/- mice, administration of magnolol induced GDF-15 production and partially suppressed appetite through GDF-15. These findings suggest that magnolol regulates GDF-15 expression through priming of promoter and enhancer activity, indicating its potential as a drug for the treatment of metabolic disorders.
Lignans/pharmacology* ; Growth Differentiation Factor 15/metabolism* ; Animals ; Biphenyl Compounds/pharmacology* ; Endoplasmic Reticulum Stress/drug effects* ; Activating Transcription Factor 4/genetics* ; Mice ; Humans ; Male ; Magnolia/chemistry* ; CCAAT-Enhancer-Binding Proteins/genetics* ; Mice, Inbred C57BL