BACKGROUND: Knee osteoarthritis (OA) is still challenging to prevent or treat. Enhanced endoplasmic reticulum (ER) stress and increased pyroptosis in chondrocytes may be responsible for cartilage degeneration. This study aims to investigate the effect of ER stress on chondrocyte pyroptosis and the upstream regulatory mechanisms, which have rarely been reported. METHODS: The expression of the histone methyltransferase enhancer of zeste homolog 2 (EZH2), microRNA-142-3p (miR-142-3p), and high mobility group box 1 (HMGB1) and the levels of ER stress, pyroptosis, and metabolic markers in normal and OA chondrocytes were investigated by western blotting, quantitative polymerase chain reaction, immunohistochemistry, fluorescence in situ hybridization, fluorescein amidite-tyrosine-valine-alanine-aspartic acid-fluoromethyl ketone (FAM-YVAD-FMK)/Hoechst 33342/propidium iodide (PI) staining, lactate dehydrogenase (LDH) release assays, and cell viability assessments. The effects of EZH2, miR-142-3p, and HMGB1 on ER stress and pyroptosis and the hierarchical regulatory relationship between them were analyzed by chromatin immunoprecipitation, luciferase reporters, gain/loss-of-function assays, and rescue assays in interleukin (IL)-1β-induced OA chondrocytes. The mechanistic contribution of EZH2, miR-142-3p, and HMGB1 to chondrocyte ER stress and pyroptosis and therapeutic prospects were validated radiologically, histologically, and immunohistochemically in surgically induced OA rats. RESULTS: Increased EZH2 and HMGB1, decreased miR-142-3p, enhanced ER stress, and activated pyroptosis in chondrocytes were associated with OA occurrence and progression. EZH2 and HMGB1 exacerbated and miR-142-3p alleviated ER stress and pyroptosis in OA chondrocytes. EZH2 transcriptionally silenced miR-142-3p via H3K27 trimethylation, and miR-142-3p posttranscriptionally silenced HMGB1 by targeting the 3'-UTR of the HMGB1 gene. Moreover, ER stress mediated the effects of EZH2, miR-142-3p, and HMGB1 on chondrocyte pyroptosis. In vivo experiments mechanistically validated the hierarchical regulatory relationship between EZH2, miR-142-3p, and HMGB1 and their effects on chondrocyte ER stress and pyroptosis. CONCLUSIONS A novel EZH2/miR-142-3p/HMGB1 axis mediates chondrocyte pyroptosis and cartilage degeneration by regulating ER stress in OA, contributing novel mechanistic insights into OA pathogenesis and providing potential targets for future therapeutic research.
Enhancer of Zeste Homolog 2 Protein/genetics* ; Osteoarthritis, Knee/pathology* ; Chondrocytes/metabolism* ; Pyroptosis/physiology* ; HMGB1 Protein/genetics* ; MicroRNAs/metabolism* ; Endoplasmic Reticulum Stress/genetics* ; Humans ; Animals ; Rats ; Male ; Rats, Sprague-Dawley ; Middle Aged

This study aims to explore the mechanism through which Yishen Jiangtang Decoction(YSJTD) regulates endoplasmic reticulum stress(ERS)-mediated NOD-like receptor thermal protein domain associated protein 3(NLRP3) inflammasome to improve diabetic nephropathy(DN) in db/db mice. Thirty db/db mice were randomly divided into the model group, YSJTD group, ERS inhibitor 4-phenylbutyric acid(4-PBA) group, with 10 mice in each group. Additionally, 10 db/m mice were selected as the control group. The YSJTD group was orally administered YSJTD at a dose of 0.01 mL·g~(-1), the 4-PBA group was orally administered 4-PBA at a dose of 0.5 mg·g~(-1), and the control and model groups were given an equal volume of carboxylmethyl cellulose sodium. The treatments were administered once daily for 8 weeks. Food intake, water consumption, and body weight were recorded every 2 weeks. After the intervention, fasting blood glucose(FBG), glycosylated hemoglobin(HbA1c), urine microalbumin(U-mALB), 24-hour urine volume, serum creatinine(Scr), and blood urea nitrogen(BUN) were measured. Inflammatory markers interleukin-1β(IL-1β) and interleukin-18(IL-18) were detected using the enzyme-linked immunosorbent assay(ELISA). Renal pathology was assessed through hematoxylin-eosin(HE), periodic acid-Schiff(PAS), and Masson staining, and transmission electron microscopy(TEM). Western blot was used to detect the expression levels of glucose-regulated protein 78(GRP78), C/EBP homologous protein(CHOP), NLRP3, apoptosis-associated speck-like protein containing CARD(ASC), cysteinyl aspartate-specific proteinase(caspase-1), and gasdermin D(GSDMD) in kidney tissues. The results showed that compared to the control group, the model group exhibited poor general condition, increased weight and food and water intake, and significantly higher levels of FBG, HbA1c, U-mALB, kidney index, 24-hour urine volume, IL-1β, and IL-18. Compared to the model group, the YSJTD and 4-PBA groups showed improved general condition, increased body weight, decreased food intake, and lower levels of FBG, U-mALB, kidney index, 24-hour urine volume, and IL-1β. Specifically, the YSJTD group showed a significant reduction in IL-18 levels compared to the model group, while the 4-PBA group exhibited decreased water intake and HbA1c levels compared to the model group. Although there was a decreasing trend in water intake and HbA1c in the YSJTD group, the differences were not statistically significant. No significant differences were observed in BUN, Scr, and kidney weight among the groups. Renal pathology revealed that the model group exhibited more severe renal damage compared to the control group. Kidney sections from the model group showed diffuse mesangial proliferation in the glomeruli, tubular edema, tubular dilation, significant inflammatory cell infiltration in the interstitium, and increased glycogen staining and blue collagen deposition in the basement membrane. In contrast, the YSJTD and 4-PBA groups showed varying degrees of improvement in renal damage, glycogen staining, and collagen deposition, with the YSJTD group showing more significant improvements. TEM analysis indicated that the model group had extensive cytoplasmic edema, homogeneous thickening of the basement membrane, fewer foot processes, and widening of fused foot processes. In the YSJTD and 4-PBA groups, cytoplasmic swelling of renal tissues was reduced, the basement membrane remained intact and uniform, and foot process fusion improved.Western blot results indicated that compared to the control group, the model group showed upregulation of GRP78, CHOP, GSDMD, NLRP3, ASC, and caspase-1 expression. In contrast, both the YSJTD and 4-PBA groups showed downregulation of these markers compared to the model group. These findings suggest that YSJTD exerts a protective effect against DN by alleviating NLRP3 inflammasome activation through the inhibition of ERS, thereby improving the inflammatory response in db/db DN mice.
Animals ; Endoplasmic Reticulum Stress/drug effects* ; Diabetic Nephropathies/metabolism* ; NLR Family, Pyrin Domain-Containing 3 Protein/genetics* ; Drugs, Chinese Herbal/administration & dosage* ; Mice ; Inflammasomes/drug effects* ; Male ; Kidney/pathology* ; Endoplasmic Reticulum Chaperone BiP ; Humans ; Interleukin-18/genetics* ; Mice, Inbred C57BL

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

Acute kidney injury (AKI) is a clinical syndrome characterized by a rapid decline in renal function. Renal ischemia-reperfusion injury (RIRI) is one of the main causes of AKI with the underlying mechanism incompletely clarified. The liver X receptors (LXRs), including LXRα and LXRβ, are members of the nuclear receptor superfamily. It has been shown that LXRs play an important role in regulating glucose and lipid metabolism, cholesterol efflux, and inflammation. The purpose of this study was to explore the role and mechanism of LXRs in RIRI. We determined the effects of LXR activation on renal function and histological changes in a mouse RIRI model and a cellular model of hypoxia/reoxygenation (H/R). In vivo results showed that LXRs agonist GW3965 significantly inhibited the increase of serum creatinine and urea nitrogen levels induced by RIRI. Both HE and PAS staining of kidney tissues revealed that GW3965 alleviated the morphological damages caused by RIRI. Immunohistochemical staining showed that GW3965 mitigated 4-HNE and GRP78 levels induced by RIRI. Furthermore, TUNEL assay indicated that GW3965 reduced RIRI-induced renal cell apoptosis. Quantitative real-time PCR (qPCR) analysis revealed that GW3965 attenuated RIRI-induced IL-6 and IL-1β mRNA expression. Compared with wild-type group, LXRα gene deficiency had little effect on RIRI-associated renal functional decline and morphological damages. Additionally, in vitro study demonstrated that GW3965 alleviated H/R-induced decrease of HK-2 human renal proximal tubule cell viability and restored the activity of superoxide dismutase (SOD) after H/R. Western blot results showed that GW3965 mitigated the increase of 4-HNE and GRP78 protein expression levels after H/R; However, knockdown of LXRβ using the small interfering RNA (siRNA) technique reduced cell viability compared to GW3965-treated group. Taken together, the LXRs agonist GW3965 significantly alleviates RIRI in mice possibly by reducing apoptosis, oxidative stress, endoplasmic reticulum stress and inflammation. These results also preliminarily confirm that the renal protective effects of LXRs agonists are dependent on LXRβ.
Animals ; Liver X Receptors/genetics* ; Reperfusion Injury/prevention & control* ; Mice ; Benzoates/pharmacology* ; Benzylamines/pharmacology* ; Male ; Endoplasmic Reticulum Chaperone BiP ; Mice, Inbred C57BL ; Apoptosis ; Acute Kidney Injury/prevention & control* ; Kidney/pathology* ; Humans

OBJECTIVES: Over 25% of the global population is affected by metabolic dysfunction-associated fatty liver disease (MAFLD), yet its pathogenesis remains unclear. Endoplasmic reticulum stress (ERS) may be involved in the onset and progression of MAFLD. Adenosine 5'-monophosphate-activated protein kinase α2 (AMPKα2), a key regulator of hepatic energy metabolism, may influence MAFLD development via ERS modulation. This study aims to investigate the role of AMPKα2 in a high-fat diet-induced MAFLD mouse model and its regulatory effect on the inositol-requiring enzyme 1 alpha (IRE1α)-c-Jun N-terminal kinase (JNK) signaling pathway. METHODS: Liver-specific AMPKα2 knockout mice on a C57BL/6 background were generated and subjected to MAFLD induction. Mice were divided into four groups: wild-type control (WT+Chow, basic diet for 12 weeks), wild-type high-fat diet (WT+HFD, high-fat diet for 12 weeks), AMPKα2 knockout control (AMPKα2 KO+Chow), and AMPKα2 knockout high-fat diet (AMPKα2 KO+HFD). Blood glucose, lipid levels, and liver function were assessed post-treatment. Liver histology was analyzed using Oil Red O, hematoxylin-eosin, Masson, and Sirius Red staining. Western blotting was used to evaluate the expression of AMPKα2, ERS markers, autophagy, apoptosis, and ferroptosis-related proteins. RESULTS: Compared with the WT+Chow group, the WT+HFD group showed significantly elevated blood glucose, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) levels (all P<0.01); histological analyses revealed hepatic steatosis, vacuolization, and fibrosis, with a significantly increased non-alcoholic steatohepatitis activity score (NAS) (P<0.001). Phosphorylated IRE1α and the autophagy marker microtubule-associated protein light chain (LC) 3II/LC3I were markedly upregulated, while apoptotic proteins (Cleaved-Caspase 3, BAX, Bcl-2) and ferroptosis markers (SLC7A11, GPX4) showed no significant change (P>0.05). In the AMPKα2 KO+HFD group, blood glucose, ALT, and AST levels were significantly reduced compared to the WT+HFD group. Histological improvements were observed with reduced vacuolization and lipid accumulation. Expression of p-IRE1α, JNK, and LC3II/LC3I was significantly decreased (P<0.05). CONCLUSIONS Hepatic AMPKα2 knockout alleviates high-fat induced MAFLD, potentially by inhibiting the IRE1α-JNK pathway and reducing autophagy.
Animals ; AMP-Activated Protein Kinases/physiology* ; Protein Serine-Threonine Kinases/metabolism* ; Mice, Knockout ; Diet, High-Fat/adverse effects* ; Mice, Inbred C57BL ; Mice ; Endoplasmic Reticulum Stress ; Endoribonucleases/metabolism* ; Male ; Liver/pathology* ; Non-alcoholic Fatty Liver Disease/metabolism* ; MAP Kinase Signaling System/physiology* ; Fatty Liver/metabolism* ; Signal Transduction

Preeclampsia and intrauterine growth restriction (IUGR) of the fetus are the two most common pregnancy complications worldwide, affecting 5%-10% of pregnant women. Preeclampsia is associated with significantly increased maternal and fetal morbidity and mortality. Hypoxia-induced uteroplacental dysfunction is now recognized as a key pathological factor in preeclampsia and IUGR. Reduced oxygen supply (hypoxia) disrupts mitochondrial and endoplasmic reticulum (ER) function. Hypoxia has been shown to alter mitochondrial reactive oxygen species (ROS) homeostasis and induce ER stress. Hypoxia during pregnancy is associated with excessive production of ROS in the placenta, leading to oxidative stress. Oxidative stress occurs in a number of human diseases, including high blood pressure during pregnancy. Studies have shown that uterine placental tissue/cells in preeclampsia and IUGR show high levels of oxidative stress, which plays an important role in the pathogenesis of both the complications. This review summarizes the role of hypoxia-induced mitochondrial oxidative stress and ER stress in the pathogenesis of preeclampsia/IUGR and discusses the potential therapeutic strategies targeting oxidative stress to treat both the pregnancy complications.
Pregnancy ; Female ; Humans ; Placenta ; Fetal Growth Retardation/etiology* ; Pre-Eclampsia/pathology* ; Reactive Oxygen Species ; Hypoxia/pathology* ; Pregnancy Complications/pathology* ; Endoplasmic Reticulum Stress

Objective: To investigate the clinical value of plasma scaffold protein SEC16A level and related models in the diagnosis of hepatitis B virus-related liver cirrhosis (HBV-LC) and hepatocellular carcinoma (HBV-HCC). Methods: Patients with HBV-LC and HBV-HCC and a healthy control group diagnosed by clinical, laboratory examination, imaging, and liver histopathology at the Third Hospital of Hebei Medical University between June 2017 and October 2021 were selected. Plasma SEC16A level was detected using an enzyme-linked immunosorbent assay (ELISA). Serum alpha-fetoprotein (AFP) was detected using an electrochemiluminescence instrument. SPSS 26.0 and MedCalc 15.0 statistical software were used to analyze the relationship between plasma SEC16A levels and the occurrence and development of liver cirrhosis and liver cancer. A sequential logistic regression model was used to analyze relevant factors. SEC16A was established through a joint diagnostic model. Receiver operating characteristic curve was used to evaluate the clinical efficacy of the model for liver cirrhosis and hepatocellular carcinoma diagnosis. Pearson correlation analysis was used to identify the influencing factors of novel diagnostic biomarkers. Results: A total of 60 cases of healthy controls, 60 cases of HBV-LC, and 52 cases of HBV-HCC were included. The average levels of plasma SEC16A were (7.41 ± 1.66) ng/ml, (10.26 ± 1.86) ng/ml, (12.79 ± 1.49) ng /ml, respectively, with P < 0.001. The sensitivity and specificity of SEC16A in the diagnosis of liver cirrhosis and hepatocellular carcinoma were 69.44% and 71.05%, and 89.36% and 88.89%, respectively. SEC16A, age, and AFP were independent risk factors for the occurrence of HBV-LC and HCC. SAA diagnostic cut-off values, sensitivity, and specificity were 26.21 and 31.46, 77.78% and 81.58%, and 87.23% and 97.22%, respectively. The sensitivity and specificity for HBV-HCC early diagnosis were 80.95% and 97.22%, respectively. Pearson correlation analysis showed that AFP level was positively correlated with alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBil), and γ-glutamyltransferase (GGT) with P < 0.01, while the serum SEC16A level was only slightly positively correlated with ALT and AST in the liver cirrhosis group (r = 0.268 and 0.260, respectively, P < 0.05). Conclusion: Plasma SEC16A can be used as a diagnostic marker for hepatitis B-related liver cirrhosis and hepatocellular carcinoma. SEC16A, combined with age and the AFP diagnostic model with SAA, can significantly improve the rate of HBV-LC and HBV-HCC early diagnosis. Additionally, its application is helpful for the diagnosis and differential diagnosis of the progression of HBV-related diseases.
Humans ; Carcinoma, Hepatocellular/pathology* ; Liver Neoplasms/pathology* ; alpha-Fetoproteins/metabolism* ; Endoplasmic Reticulum/metabolism* ; Golgi Apparatus/metabolism* ; Vesicular Transport Proteins ; Liver Cirrhosis/complications* ; Hepatitis B/complications* ; ROC Curve ; Hepatitis B virus/metabolism* ; Biomarkers, Tumor

Epilepsies are a group of chronic neurological disorders characterized by spontaneous recurrent seizures caused by abnormal synchronous firing of neurons and transient brain dysfunction. The underlying mechanisms are complex and not yet fully understood. Endoplasmic reticulum (ER) stress, as a condition of excessive accumulation of unfolded and/or misfolded proteins in the ER lumen, has been considered as a pathophysiological mechanism of epilepsy in recent years. ER stress can enhance the protein processing capacity of the ER to restore protein homeostasis through unfolded protein response, which may inhibit protein translation and promote misfolded protein degradation through the ubiquitin-proteasome system. However, persistent ER stress can also cause neuronal apoptosis and loss, which may aggravate the brain damage and epilepsy. This review has summarized the role of ER stress in the pathogenesis of genetic epilepsy.
Humans ; Endoplasmic Reticulum Stress/genetics* ; Unfolded Protein Response ; Endoplasmic Reticulum/pathology* ; Apoptosis ; Epilepsy/genetics*

OBJECTIVE: To investigate the effect of melatonin (MLT) on the proliferation and apoptosis of human multiple myeloma cell line RPMI 8226 and its possible mechanism. METHODS: RPMI 8226 cells were cultured in vitro, and different concentrations of MLT were treated on RPMI 8226 cells. The effects of MLT on RPMI 8226 cell proliferation were detected by CCK-8 assay and methylcellulose cloning assay, and the effects of MLT on cell apoptosis were detected by AnnexinV-FITC /PI, flow cytometry. Western blot was used to determine the expression of apoptosis and endoplasmic reticulum stress-related proteins in each group, and CCK-8 assay was used to determine the effect of MLT combined with bortezemib on the viability of RPMI 8226 cells. RESULTS: MLT inhibited the proliferation of RPMI 8226 cells in a dose- and time-dependent manner (r=-0.9777，r=-0.9951). With the increase of MLT concentration, the number of clones decreased, the apoptosis of RPMI 8226 cells increased (P<0.05), the expression of anti-apoptotic protein XIAP decreased, the expression of apoptotic proteins Bax and Caspase3 increased, and the expression of endoplasmic reticulum stress-related proteins increased. Compared with the control group, the survival of RPMI 8226 cells in the MLT and BTZ combined group significantly decreased (P<0.01). CONCLUSION MLT can inhibit the proliferation of RPMI 8226 cells, promote the apoptosis of RPMI 8226 cells, and enhance the anti-tumor effect of BTZ on RPMI 8226 cells. The mechanism may be related to endoplasmic reticulum stress.
Apoptosis ; Cell Line, Tumor ; Cell Proliferation ; Endoplasmic Reticulum Stress ; Humans ; Melatonin/pharmacology* ; Multiple Myeloma/pathology* ; Sincalide/pharmacology*