Upregulation of GRP78 is accompanied by decreased antioxidant response and mitophagy promotion in streptozotocin-induced type 1 diabetes in rats.

Endoplasmic reticulum stress, oxidative stress, and mitochondrial dysfunction are interconnected processes involved in the pathogenesis of diabetes mellitus (DM). In the present study, we demonstrate a distinct unfolded protein response (UPR) signaling pathways in two mammalian models of DM: ß-TC-6 cell line and streptozotocin-induced type 1 diabetes model in rats. However, a feature common to both systems was the upregulation of the GRP78 protein. Moreover, in vivo studies showed the disruption of the antioxidant system and an escalation of mitophagy against the background of a depletion of the level of ATP in pancreatic cells. In conclusion, we suggest that glucotoxic conditions induced GRP78 upregulation, and next cause depletion of the antioxidant pool and disruption of the functioning of antioxidant defense enzymes and in consequence promote mitophagy in pancreatic cells. Therefore, GRP78 may be considered as a potential therapeutic factor in patients with diabetes.

Effects of Melatonin and 3,5,3'-Triiodothyronine on the Development of Rat Granulosa Cells.

Melatonin, as an endocrine neurotransmitter, can promote the development of the ovary. Meanwhile, it also has protective effect on the ovary as an antioxidant. Thyroid hormone (TH) is essential for normal human reproductive function. Many studies have shown that 3,5,3'-triiodothyronine (T3) regulates the development of ovarian granulosa cells. However, little is known about the specific mechanisms by which melatonin combines with T3 to regulate granulosa cell development. The aim of present study was to investigate the effects and the possible mechanisms of melatonin and T3 on ovarian granulosa cell development. In the present study, cell development and apoptosis were detected by CCK8, EdU and TUNEL, respectively. The levels of related proteins were analyzed by Western blotting. The results showed that oxidative stress (OS) and reactive oxygen species (ROS) were induced by H2O2 in granulosa cells, and cell apoptosis was also increased accompanied with the decreased cellular proliferation and viability. Melatonin protects granulosa cells from H2O2-induced apoptosis and OS by downregulating ROS levels, especially in the presence of T3. Co-treatment of cell with melatonin and T3 also promotes the expression of GRP78 and AMH, while inhibiting CHOP, Caspase-3, and P16. It was demonstrated that melatonin alone or in combination with T3 had positive effect on the development of granulosa cells. In addition, the AMPK/SIRT1 signaling pathway is involved in the process of melatonin/T3 promoting granulosa cell development.

Evaluation of Endoplasmic Reticulum Stress in an Experimental Intestinal Ischemia-Reperfusion Model in Rats: The Role of Ozone Therapy and Trimetazidine.

AIM: The objective of the study was to assess the impact of ozone (O3) and trimetazidine on the intestines following ischemia-reperfusion (I/R) injury through the investigation of endoplasmic reticulum stress. METHODS: Forty Sprague Dawley rats were separated into five groups. The groups were named as follows: control, O3, I/R, I/R + trimetazidine (TMZ), and I/R + O3. The control group had laparotomy and exploration of the superior mesenteric artery (SMA) only. Furthermore, alongside laparotomy and SMA exploration, an intraperitoneal (i.p.) administration of a 0.7 mg/kg ozone-oxygen (O3-O2) combination was given to the O3 group. In the experimental groups, the SMA was blocked with the silk suture ligation technique for a duration of 1 h and then restored to normal blood flow for another hour. In the I/R + O3 group, ozone was delivered i.p. at a dosage of 0.7 mg/kg, 30 min after ischemia. In the I/R + TMZ group, a dose of 20 mg/kg/day of trimetazidine was administered orally via gavage for a duration of 7 days, beginning 1 week prior to the induction of ischemia. Intestinal tissues were taken to assess indicators of intestinal mucosal injury and oxidative stress. RESULTS: The level of the lipid peroxidation marker malondialdehyde (MDA) was significantly reduced in the experimental groups as compared to the I/R group (p < 0.05). The experimental groups had considerably greater levels of glutathione (GSH), which reflects antioxidant capacity, compared to the I/R group (p < 0.05). Nevertheless, the concentration of GSH was observed to be increased in the I/R + O3 group in comparison to the I/R + TMZ group (p < 0.05). The histopathological damage score showed a substantial decrease in the experimental groups as compared to the I/R group (p < 0.05). The I/R + O3 group had the lowest injury score. The experimental groups exhibited significantly reduced positivity of the endoplasmic reticulum (ER) stress markers C/EBP homologous protein (CHOP) and glucose-regulated protein (GRP)-78 compared to the I/R group (p < 0.05). CONCLUSIONS: The findings provide evidence for the potential advantages of utilizing ozone therapy in the treatment of intestinal ischemia-reperfusion injury. Additionally, they propose that ozone should be assessed in more extensive clinical trials in the future as a therapeutic agent that can disrupt endoplasmic reticulum stress.

GRP78 exerts antiviral function against influenza A virus infection by activating the IFN/JAK-STAT signaling.

Influenza is an acute viral respiratory infection that causes mild to severe illness in humans and animals. Current studies show that glucose-regulated protein 78 (GRP78) can exert crucial functions during viral infection; however, the mechanism by which GRP78 regulates influenza A virus (IAV) infection remains unclear. In the present study, we found that IAV infection increased GRP78 expression. Overexpression of GRP78 significantly inhibited IAV replication, as indicated by reduced viral mRNA levels, protein levels, and viral titers. Mechanistically, Type I interferon (IFN) response signaling is upregulated during IAV infection by GRP78. Further study showed that GRP78 interacts with tyrosine kinase 2 (TYK2) and enhances its phosphorylation, thereby activating downstream STAT1/2 and antiviral IFN-stimulated gene (ISG) expression. Collectively, these results demonstrate an important mechanism by which GRP78 exerts in innate antiviral effect in IAV infection. This mechanism could be used as a therapeutic target for anti-influenza treatment.

Interaction Between the PERK/ATF4 Branch of the Endoplasmic Reticulum Stress and Mitochondrial One-Carbon Metabolism Regulates Neuronal Survival After Intracerebral Hemorrhage.

Recent investigations have revealed that oxidative stress can lead to neuronal damage and disrupt mitochondrial and endoplasmic reticulum functions after intracerebral hemorrhage (ICH). However, there is limited evidence elucidating their role in maintaining neuronal homeostasis. Metabolomics analysis, RNA sequencing, and CUT&Tag-seq were performed to investigate the mechanism underlying the interaction between the PERK/ATF4 branch of the endoplasmic reticulum stress (ERS) and mitochondrial one-carbon (1C) metabolism during neuronal resistance to oxidative stress. The association between mitochondrial 1C metabolism and the PERK/ATF4 branch of the ERS after ICH was investigated using transcription factor motif analysis and co-immunoprecipitation. The findings revealed interactions between the GRP78/PERK/ATF4 and mitochondrial 1C metabolism, which are important in preserving neuronal homeostasis after ICH. ATF4 is an upstream transcription factor that directly regulates the expression of 1C metabolism genes. Additionally, the GRP78/PERK/ATF4 forms a negative regulatory loop with MTHFD2 because of the interaction between GRP78 and MTHFD2. This study presents evidence of disrupted 1C metabolism and the occurrence of ERS in neurons post-ICH. Supplementing exogenous NADPH or interfering with the PERK/ATF4 could reduce symptoms related to neuronal injuries, suggesting new therapeutic prospects for ICH.

Endoplasmic Reticulum Stress in Myometrial Smooth Muscle Cells and Spontaneous Contraction Changes in the Uterus of Dehydroepiandrosterone-induced Polycystic Ovary Syndrome Rats.

Myometrial changes in polycystic ovary syndrome (PCOS) are poorly investigated. Thus, we aimed to investigate endoplasmic reticulum (ER) stress in myometrial smooth muscle cells and changes in spontaneous uterine contraction in PCOS. Twenty-one female Sprague-Dawley rats (21 days old) were divided into control (n = 7), vehicle (n = 7) and PCOS (n = 7) groups. While the control group was not injected subcutaneously, the vehicle group was injected subcutaneously with sesame oil (0.2 ml/day) for 20 consecutive days. The PCOS group was injected subcutaneously with dehydroepiandrosterone (6 mg/100 g/day dissolved in 0.2 ml sesame oil) for 20 consecutive days. Blood samples were collected for the measurement of follicle stimulating-hormone (FSH), luteinizing hormone (LH), testosterone (T), estradiol (E2) and glucose-regulated protein 78 (GRP78). The mRNA expression of GRP78 in the uterine tissue samples was analysed by quantitative real-time polymerase chain reaction. GRP78 protein expression was assessed by immunohistochemistry. Myometrial smooth muscle cells were examined by transmission electron microscopy. Uterine contractions were evaluated with isolated organ bath experiments. In the PCOS group, T and LH levels increased significantly, although FSH and E2 levels decreased, but this decrease was not statistically significant. Additionally, GRP78 levels increased significantly in the PCOS group. In the PCOS group, the mRNA level, immunostaining intensity of GRP78, and ER damage grade increased, but the uterine tissue calcium levels, and the frequency and amplitude of spontaneous uterine contractions decreased. The results indicated that increased ER stress in myometrial smooth muscle cells may play a causative role in the decreased spontaneous uterine contractions in PCOS.

Targeting stress induction of GRP78 by cardiac glycoside oleandrin dually suppresses cancer and COVID-19.

BACKGROUND: Despite recent therapeutic advances, combating cancer resistance remains a formidable challenge. The 78-kilodalton glucose-regulated protein (GRP78), a key stress-inducible endoplasmic reticulum (ER) chaperone, plays a crucial role in both cancer cell survival and stress adaptation. GRP78 is also upregulated during SARS-CoV-2 infection and acts as a critical host factor. Recently, we discovered cardiac glycosides (CGs) as novel suppressors of GRP78 stress induction through a high-throughput screen of clinically relevant compound libraries. This study aims to test the possibility that agents capable of blocking stress induction of GRP78 could dually suppress cancer and COVID-19. RESULTS: Here we report that oleandrin (OLN), is the most potent among the CGs in inhibiting acute stress induction of total GRP78, which also results in reduced cell surface and nuclear forms of GRP78 in stressed cells. The inhibition of stress induction of GRP78 is at the post-transcriptional level, independent of protein degradation and autophagy and may involve translational control as OLN blocks stress-induced loading of ribosomes onto GRP78 mRNAs. Moreover, the human Na+/K+-ATPase α3 isoform is critical for OLN suppression of GRP78 stress induction. OLN, in nanomolar range, enhances apoptosis, sensitizes colorectal cancer cells to chemotherapeutic agents, and reduces the viability of patient-derived colon cancer organoids. Likewise, OLN, suppresses GRP78 expression and impedes tumor growth in an orthotopic breast cancer xenograft model. Furthermore, OLN blocks infection by SARS-CoV-2 and its variants and enhances existing anti-viral therapies. Notably, GRP78 overexpression mitigates OLN-mediated cancer cell apoptotic onset and suppression of virus release. CONCLUSION: Our findings validate GRP78 as a target of OLN anti-cancer and anti-viral activities. These proof-of-principle studies support further investigation of OLN as a readily accessible compound to dually combat cancer and COVID-19.

Expression of Autophagy Markers LC3B, LAMP2A, and GRP78 in the Human Kidney during Embryonic, Early Fetal, and Postnatal Development and Their Significance in Diabetic Kidney Disease.

Autophagy is the primary intracellular degradation system, and it plays an important role in many biological and pathological processes. Studies of autophagy involvement in developmental processes are important for understanding various processes. Among them are fibrosis, degenerative diseases, cancer development, and metastasis formation. Diabetic kidney disease is one of the main causes of chronic kidney disease and end-stage renal failure. The aim of this study was to investigate the immunohistochemical expression patterns of LC3B, LAMP2A, and GRP78 during different developmental stages of early-developing human kidneys and in samples from patients with type II diabetes mellitus. During the 7/8th DW, moderate expression of LC3B and LAMP2A and strong expression of GRP78 were found in the mesonephric glomeruli and tubules. In the 9/10th DW, the expression of LC3B and LAMP2A was even more pronounced in the mesonephric tubules. LC3B, LAMP2A, and GRP78 immunoreactivity was also found in the paramesonephric and mesonephric ducts and was stronger in the 9/10th DW compared with the 7/8th DW. In addition, the expression of LC3B, LAMP2A, and GRP78 also appeared in the mesenchyme surrounding the paramesonephric duct in the 9/10th DW. In the 15/16th DW, the expression of LC3B in the glomeruli was weak, that of LAMP2A was moderate, and that of GRP78 was strong. In the tubuli, the expression of LC3B was moderate, while the expression of LAMP2A and GRP78 was strong. The strongest expression of LC3B, LAMP2A, and GRP78 was observed in the renal medullary structures, including developing blood vessels. In postnatal human kidneys, the most extensive LC3B, LAMP2A, and GRP78 expression in the cortex was found in the epithelium of the proximal convoluted tubules, with weak to moderate expression in the glomeruli. The medullary expression of LC3B was weak, but the expression of LAMP2A and GRP78 was the strongest in the medullary tubular structures. Significantly lower expression of LC3B was found in the glomeruli of the diabetic patients in comparison with the nondiabetic patients, but there was no difference in the expression of LC3B in the tubule-interstitial compartment. The expression of LAMP2A was significantly higher in the tubule-interstitial compartments of the diabetic patients in comparison with the nondiabetic patients, while its expression did not differ in the glomeruli. Extensive expression of GRP78 was found in the glomeruli and the tubule-interstitial compartments, but there was no difference in the expression between the two groups of patients. These data give us new information about the expression of LC3B, LAMP2A, and GRP78 during embryonic, fetal, and early postnatal development. The spatiotemporal expression of LC3B, LAMP2A, and GRP78 indicates the important role of autophagy during the early stages of renal development. In addition, our data suggest a disturbance in autophagy processes in the glomeruli and tubuli of diabetic kidneys as an important factor in the pathogenesis of diabetic kidney disease.

The Functions of SARS-CoV-2 Receptors in Diabetes-Related Severe COVID-19.

Angiotensin-converting enzyme 2 (ACE2) is considered a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor of high importance, but due to its non-ubiquitous expression, studies of other proteins that may participate in virus internalisation have been undertaken. To date, many alternative receptors have been discovered. Their functioning may provide an explanation for some of the events observed in severe COVID-19 that cannot be directly explained by the model in which ACE2 constitutes the central point of infection. Diabetes mellitus type 2 (T2D) can induce severe COVID-19 development. Although many mechanisms associated with ACE2 can lead to increased SARS-CoV-2 virulence in diabetes, proteins such as basigin (CD147), glucose-regulated protein 78 kDa (GRP78), cluster of differentiation 4 (CD4), transferrin receptor (TfR), integrins α5ß1/αvß3, or ACE2 co-receptors neuropilin 2 (NRP2), vimentin, and even syalilated gangliosides may also be responsible for worsening the COVID-19 course. On the other hand, some others may play protective roles. Understanding how diabetes-associated mechanisms can induce severe COVID-19 via modification of virus receptor functioning needs further extensive studies.

Deoxypodophyllotoxin Mediates Autophagy Death through Inhibition of GRP78 in Human Osteosarcoma.

BACKGROUND: Glucose-regulated protein 78 (GRP78), as a chaperone protein, can protect the endoplasmic reticulum of cells and is expressed to influence chemoresistance and prognosis in cancer. Deoxypodophyllotoxin (DPT) is a compound with antitumor effects on cancers. DPT inhibits the proliferation of osteosarcoma by inducing apoptosis, necrosis, or cell cycle arrest. OBJECT: This study was performed to demonstrate the molecular mechanism by which DPT attenuates osteosarcoma progression through GRP78. METHODS: Natural compound libraries and western blot (WB) were used to screen the inhibitors of osteosarcoma GRP78. The expression of mitochondria-related genes in cancer cells of the treatment group was detected by quantitative real-time PCR (qPCR) and WB. 3-(4,5)- Dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) and 5-ethynyl-2'- deoxyuridine (EDU) were used to discover the activity and proliferation of osteosarcoma cells treated with DPT. We constructed an in vivo mouse model of DPT drug therapy and carried out immunohistochemical detection of xenografts. The treated osteosarcoma cells were analyzed using bioinformatics and electron microscopy. The data were analyzed finally. RESULTS: DPT inhibited osteosarcoma cell survival and the growth of tumor xenografts. It promoted up-regulation of BCL2-associated X protein (Bax) and B-cell CLL/lymphoma 2 (Bcl-2), which serves to mediate and attenuate, respectively, the killing activities of DPT through mitochondria dysfunction. The effect of DPT against cancer cells could be attenuated by the overexpression of GRP78, characterized by the inactivation of the caspase cascade. The loss of GRP78 in osteosarcoma cells negatively mediated the basal level of autophagyassociated genes. DPT stimulated autophagy via the phosphoinositide 3-kinase (PI3K)-v-akt murine thymoma viral oncogene homolog (AKT), a mechanistic target of rapamycin (mTOR) axis. The autophagy caused by DPT played an active role in the osteosarcoma of humans and blocked the apoptotic cascade. CONCLUSION: Combination treatment with the GRP78 inhibitor DPT and pharmacological autophagy inhibitors will be a meaningful method of obviating osteosarcoma cells.

Effect of kangaroo mother care and white noise on physiological-stress parameters in heel lancing: randomized controlled study.

BACKGROUND: Newborns are exposed to varying degrees of stressful interventions due to procedures such as heel lancing used in routine metabolic screenings. It is an examination of the effects of white noise and kangaroo care on some physiological parameters and stress markers (cortisol and glucose-regulated protein 78-GRP78) in heel lancing in newborns. METHODS: Randomized controlled study was conducted at a gynecology service of a hospital between January and September 2023. 90 babies were divided into three groups: 30 babies in the Kangaroo Care Group (KCG), 30 babies in the White Music Group (WMG), and 30 babies in the Control Group (CG). All babies were randomly divided into groups. Stress parameters were measured by saliva collection method and physiological parameters by saturation device. RESULTS: A statistically significant difference was determined between the total crying time, pulse and saturation values ​​according to the groups (p < 0.001; p = 0.001). A statistically significant difference was determined between the mean values ​​of cortisol and GRP78 measurements according to group and time interaction (p < 0.001). KCG was more effective in reducing total crying time and stabilizing pulse, saturation, salivary cortisol, GRP-78 values compared to WNG and CG. CONCLUSION: It was concluded that white noise and kangaroo care help reduce newborns' stress in the case of heel lancing. PRACTICAL IMPLICATIONS: The practice of kangaroo care and the use of white noise methods may assist healthcare professionals as supportive methods in stress management during invasive procedures. TRIAL REGISTRATION: NCT06278441, registered on 19/02/2024.

Recruitment of USP10 by GCS1 to deubiquitinate GRP78 promotes the progression of colorectal cancer via alleviating endoplasmic reticulum stress.

BACKGROUND: Long-term accumulation of misfolded proteins leads to endoplasmic reticulum (ER) stress in colorectal cancer (CRC). However, the precise pathways controlling the decision between survival and apoptosis in CRC are unclear. Therefore, in this study, we investigated the function and molecular mechanism of glucosidase I (GCS1) in regulating ER stress in CRC. METHODS: A public database was used to confirm the expression level of GCS1 in CRC and normal tissues. Clinical samples from our center were used to confirm the mRNA and protein expression levels of GCS1. Cell proliferation, migration, invasion, and apoptosis assays revealed the biological role of GCS1. Immunohistochemical techniques were used to evaluate the expression of key proteins in subcutaneous implanted tumors in nude mice, which provided further evidence for the biological function of GCS1 in promoting cancer in vivo. The results of coimmunoprecipitation-mass spectrometry analysis and immunofluorescence colocalization analysis the interaction between GCS1 and GRP78. In addition, the mechanism of action of USP10, GRP78, and GCS1 at the post- translational level was investigated. Finally, a tissue microarray was used to examine the connection between GCS1 and GRP78 expression and intracellular localization of these proteins using immunohistochemistry and immunofluorescence. RESULTS: The experimental results revealed that GCS1 was substantially expressed in CRC, with higher expression indicating a worse prognosis. Thus, GCS1 can enhance the proliferation and metastasis while inhibiting the apoptosis of CRC cells both in vivo and in vitro. Mechanistically, GCS1 binds to GRP78, recruits USP10 for deubiquitination of GRP78 to promote its degradation, and decreases ER stress-mediated apoptosis, increasing CRC cell proliferation and metastasis. CONCLUSIONS: In summary, GCS1 stimulates CRC growth and migration and reduces ER stress-mediated apoptosis via USP10-mediated deubiquitination of GRP78. Our findings identify a possible therapeutic target for CRC.

BRD4 absence inactivates endoplasmic reticulum stress to retard dehydroepiandrosterone-triggered ovarian granular cell apoptosis in polycystic ovary syndrome via GRP78.

Polycystic ovary syndrome (PCOS) is a hormonal disorder and significantly affects reproductive and metabolic function. Bromodomain-containing protein 4 (BRD4) is reported to promote ovarian fibrosis in PCOS. The present work was conducted to investigate the detailed role of BRD4 and the corresponding functional mechanism in PCOS. Functional experiments including CCK-8 method, EDU staining and TUNEL staining were used to detect the key cellular processes. Western blot examined the expression of BRD4, apoptosis- and endoplasmic reticulum stress (ERS)-associated proteins. HDOCK server predicted the binding of BRD4 with Glucose-Regulated Protein 78 (GRP78), which was validated by Co-IP assay. BRD4 expression was increased and ERS was activated in dehydroepiandrosterone (DHEA)-induced KGN cells. Inhibition of BRD4 improved the viability whereas it inhibited the apoptosis and ERS of KGN cells induced by DHEA. In addition, BRD4 bound to GRP78. GRP78 elevation or ERS activator tunicamycin (TM) partly abolished the impacts of BRD4 silencing on the ERS, proliferation and apoptosis in DHEA-treated KGN cells. Anyway, knockdown of BRD4 may reduce DHEA-induced ovarian granular cell damage in PCOS via inactivating GRP78-mediated ERS.

Small molecules targeting GRP78 mitigate anti-GRP78 autoantibody-mediated tissue factor procoagulant activity in cultured endothelial cells.

BACKGROUND: The 78-kDa glucose-regulated protein (GRP78) expressed on the cell surface (csGRP78) has been reported to regulate tissue factor (TF) procoagulant activity (PCA) in lesion-resident endothelial cells (ECs), which is further enhanced by circulating anti-GRP78 autoantibodies that bind to the Leu98-Leu115 epitope in GRP78. OBJECTIVES: Determine the effects of the engagement of the anti-GRP78 autoantibody to csGRP78 on ECs and the underlying mechanisms that impact TF PCA. METHODS: Immunofluorescent staining was used to determine the presence of csGRP78 in tumor necrosis factor α-treated ECs. An established TF PCA assay was used to evaluate human ECs following treatment with anti-GRP78 autoantibodies. The Fura 2-AM assay (Abcam) was used to quantify changes in intracellular Ca2+ levels. Small molecules predicted to bind GRP78 were identified using artificial intelligence. Enzyme-linked immunosorbent assays were used to assess the ability of these GRP78 binders to mitigate TF activity and interfere with the autoantibody/csGRP78 complex. RESULTS: In tumor necrosis factor α-treated ECs, anti-GRP78 autoantibodies increased TF PCA. This observation was further enhanced by endoplasmic reticulum stress-induced elevation of csGRP78 levels. Anti-GRP78 autoantibody treatment increased intracellular Ca2+ levels. Sequestering the anti-GRP78 autoantibody with a conformational peptide or blocking with heparin attenuated anti-GRP78 autoantibody-induced TF PCA. We identified B07∗, as a GRP78 binder that diminished anti-GRP78 autoantibody-induced TF PCA on ECs. CONCLUSION: These findings show how anti-GRP78 autoantibodies enhance TF PCA that contributes to thrombosis and identify novel GRP78 binders that represent a potential novel therapeutic strategy for treating and managing atherothrombotic disease.

Eurycomanone inhibits osteosarcoma growth and metastasis by suppressing GRP78 expression.

ETHNOPHARMACOLOGICAL RELEVANCE: Osteosarcoma (OS) is characterized by rapid growth and frequent pulmonary metastasis. Eurycoma longifolia Jack, a flowering plant primarily found in Southeast Asian countries, is commonly used in traditional herbal medicine. Its root extract is mainly used for against cancer, malaria, parasites and other conditions. The active compound in its root extract, eurycomanone (EUR), has been proven to inhibit lung and liver cancer proliferation. AIM OF THE STUDY: Our research aimed to investigate the inhibitory effect and underlying molecular mechanism of EUR on OS growth and metastasis. MATERIALS AND METHODS: In vitro experiments: western blotting (WB) screened 41 compounds that inhibited GRP78 expression and evaluated the protein levels of GRP78, PARP, cleaved-PARP, MMP2, and MMP9. Cell proliferation was evaluated using CCK-8, EdU, colony formation assay, and cell apoptosis was assessed by flow cytometry. Transwell, wound healing, and tube formation assays were performed to determine the effect of EUR on tumor invasion, migration, and angiogenesis, respectively. Quantitative real-time polymerase chain (qRT-PCR) and dual-luciferase activity assays detected GRP78 mRNA stability and transcription levels post-EUR and thapsigargin treatment. RNA-Seq identified signaling pathways inhibited by EUR. In vivo experiments: effects of EUR in mice were evaluated by H&E staining to detect lung metastasis and potential toxic effects in tissues. Immunohistochemical (IHC) staining detected the expression of Ki-67, CD31, and cleaved caspase-3 in tumors. RESULTS: GRP78 is highly expressed in OS and correlated with poor prognosis. In vitro, eurycomanone (EUR) significantly downregulated GRP78 expression, inhibited cell proliferation, migration, invasion, tube formation, and induced apoptosis. Moreover, it enhanced trichostatin A (TSA) sensitivity and exhibited inhibitory effects on other cancer types. Mechanistically, EUR decreased GRP78 mRNA stability and transcription. In vivo, EUR inhibited proliferation and invasion in tibial and PDX models. CONCLUSIONS: Our study demonstrated that EUR inhibits the growth and metastasis of OS by reducing GRP78 mRNA stability and inhibiting its transcription, which offers a novel approach for clinical treatment of OS.

Grp78 regulates NLRP3 inflammasome and participates in Sjogren's syndrome.

OBJECTIVE: The purpose of the present study was to potential effects of forsythiaside A (FA) on Sjogren's syndrome (SS). METHODS: Enzyme linked immunosorbent assay for detecting cytokines and Western blotting was used for detecting related protein expression. RESULTS: FA effectively reduced the secretion of inflammatory cytokines, the expression of Caspase-1 and NLRP3 proteins and the expression of p65 in SS. FA also effectively inhibited the high expression of Grp78 in SS. When Grp78 expression was silenced, it effectively reduced the secretion of inflammatory cytokines, the expression of Caspase-1 and NLRP3 proteins and the expression of p65 in the nucleus in SS. FA effectively inhibit the secretion of inflammatory cytokines induced by overexpression of Grp78, the expression of Caspase-1 and NLRP3 proteins and the expression of p65 in the nucleus in SS. CONCLUSION: FA induces the degradation of Grp78 protein, regulates the NF-κB signaling pathway in SS and inhibited NLRP3 inflammasome activation and reduced the release of inflammatory cytokines to alleviate SS.

Regulation of lipid metabolism in grass carp primary hepatocytes by exosomes derived from fatty hepatocytes though GRP78.

Exosomes regulate lipid metabolism by carrying miRNAs, nucleic acids, and proteins, thereby influencing the function of receptor cells. Glucose-regulated protein 78 (GRP78) is also involved in the regulation of lipid metabolism. However, it remains unclear whether exosomes derived from fatty hepatocytes (OA-Exo) regulate lipid metabolism through the enrichment of GRP78. In this study, we observed the expression of GRP78 was significantly increased in fatty hepatocytes (incubating hepatocytes with oleic acid (OA) for 24 h) and OA-Exo (P < 0.05). In addition, OA-Exo (50 µg/mL) and GRP78 protein (1 µg/mL) significant increased the content of triacylglycerol (TG) and total cholesterol (TC), as well as up-regulated the expression of GRP78 and inositol-requiring enzyme-1alpha (IRE1α) protein (P < 0.05). We further used YUM70 (an inhibitor of GRP78) to inhibit endogenous GRP78, and compared with the YUM70 group, OA-Exo reversed the effect of YUM70 and increased the content of TG, TC, and the expression of GRP78 protein in hepatocytes (P < 0.05). Furthermore, the inhibition of the IRE1α pathway with 4µ8C resulted in a significant decrease in TG content compared to the control group (P < 0.05). However, when compared with the 4µ8C group, OA-Exo and GRP78 reversed the effect of 4µ8C and significantly increased TG content (P < 0.05). Taken together, these results indicated that OA-Exo activated IRE1α to promote lipid accumulation in hepatocytes through the enrichment of GRP78. This study provided a new perspective for further exploration of exosomal lipid metabolism in fish.

GRP78 inhibitor YUM70 upregulates 4E-BP1 and suppresses c-MYC expression and viability of oncogenic c-MYC tumors.

The 78-kDa glucose regulated protein (GRP78) commonly upregulated in a wide variety of tumors is an important prognostic marker and a promising target for suppressing tumorigenesis and treatment resistance. While GRP78 is well established as a major endoplasmic reticulum (ER) chaperone with anti-apoptotic properties and a master regulator of the unfolded protein response, its new role as a regulator of oncoprotein expression is just emerging. MYC is dysregulated in about 70 % of human cancers and is the most commonly activated oncoprotein. However, despite recent advances, therapeutic targeting of MYC remains challenging. Here we identify GRP78 as a new target for suppression of MYC expression. Using multiple MYC-dependent cancer models including head and neck squamous cell carcinoma and their cisplatin-resistant clones, breast and pancreatic adenocarcinoma, our studies revealed that GRP78 knockdown by siRNA or inhibition of its activity by small molecule inhibitors (YUM70 or HA15) reduced c-MYC expression, leading to onset of apoptosis and loss of cell viability. This was observed in 2D cell culture, 3D spheroid and in xenograft models. Mechanistically, we determined that the suppression of c-MYC is at the post-transcriptional level and that YUM70 and HA15 treatment potently upregulated the eukaryotic translation inhibitor 4E-BP1, which targets eIF4E critical for c-MYC translation initiation. Furthermore, knock-down of 4E-BP1 via siRNA rescued YUM70-mediated c-MYC suppression. As YUM70 is also capable of suppressing N-MYC expression, this study offers a new approach to suppress MYC protein expression through knockdown or inhibition of GRP78.

Flow shear force destabilizes carotid plaques by affecting CHOP and GRP78 proteins.

BACKGROUND: Various factors, including blood, inflammatory, infectious, and immune factors, can cause ischemic stroke. However, the primary cause is often the instability of cervical arteriosclerosis plaque. It is estimated that 18-25% of ischemic strokes are caused by the rupture of carotid plaque.1 Plaque stability is crucial in determining patient prognosis. Developing a highly accurate, non-invasive, or minimally invasive technique to assess carotid plaque stability is crucial for diagnosing and treating stroke.Previous research by our group has demonstrated that the expression levels of CHOP (C/EBP homologous protein) and GRP78 (glucose-regulated protein 78) are correlated with the stability of atherosclerotic plaques.2 OBJECT: This research assesses changes in GRP78 and CHOP expressions in human umbilical vein endothelial cells(HUVEC) following experiments within the hemodynamic influencing factors test system. Additionally, it includes conducting an empirical study on the impact of blood flow shear force on the stability of human carotid atherosclerotic plaques. The objective is to explore the implications of blood flow shear force on the stability of carotid atherosclerotic plaques. METHOD: The hemodynamic influencing factors test bench system was configured with low (Group A, 4 dyns/cm²), medium (Group B, 8 dyns/cm²), and high shear force groups (Group C, 12 dyns/cm²). Relative expression levels of GRP78 and CHOP proteins in human umbilical vein endothelial cells were measured using Western blot analysis, and quantitative analysis of GRP78 and CHOP mRNA was conducted using RT-qPCR. Meanwhile, plaques from 60 carotid artery patients, retrieved via Carotid Endarterectomy (CEA), were classified into stable (S) and unstable (U) groups based on pathological criteria. Shear force at the carotid bifurcation was measured preoperatively using ultrasound. Western blot and RT-qPCR were used to analyze the relative expression levels of GRP78 and CHOP proteins and mRNA, respectively, in the plaque specimens from both groups. RESULT: Expression levels of GRP78, CHOP proteins, and their mRNAs were assessed in groups A, B, and C via Western blot and RT-qPCR. Results showed that in the low-shear group, all markers were elevated in group A compared to groups B and C. Statistical analysis revealed significantly lower shear forces at the carotid bifurcation in group U compared to group S. In group U plaques, GRP78 and CHOP expressions were significantly higher in group U than in group S. CONCLUSION: Blood flow shear forces variably affect the expression of GRP78 and CHOP proteins, as well as their mRNA levels, in vascular endothelial cells. The lower the shear force and fluid flow rate, the higher the expression of GRP78 and CHOP, potentially leading to endoplasmic reticulum stress(ERS), which may destabilize the plaque.

Short and long-term 2100 MHz radiofrequency radiation causes endoplasmic reticulum stress in rat testis.

Long-term radiofrequency radiation (RFR) exposure, which adversely affects organisms, deteriorates testicular functions. Misfolding or unfolding protein accumulation in the endoplasmic reticulum (ER) initiates an intracellular reaction known as ER stress (ERS), which activates the unfolded protein response (UPR) for proteostasis. Since both RFR exposure and ERS can cause male infertility, we hypothesized that RFR exposure causes ERS to adversely affect testicular functions in rats. To investigate role of ERS in mediating RFR effects on rat testis, we established five experimental groups in male rats: control, short-term 2100-megahertz (MHz) RFR (1-week), short-term sham (sham/1-week), long-term 2100-MHz RFR (10-week), and long-term sham (sham/10-week). ERS markers Grp78 and phosphorylated PERK (p-Perk) levels and ERS-related apoptosis markers Chop and caspase 12 were investigated by immunohistochemistry, immunoblotting, and quantitative real-time polymerase chain reaction (qPCR). Long-term RFR exposure increased Grp78, p-Perk, and Chop levels, while short-term RFR exposure elevated Chop and caspase 12 levels. Chop expression was not observed in spermatogonia and primary spermatocytes, which may protect spermatogonia and primary spermatocytes against RFR-induced ERS-mediated apoptosis, thereby allowing transmission of genetic material to next generations. While short and long-term RFR exposures trigger ERS and ERS-related apoptotic pathways, further functional analyses are needed to elucidate whether this RFR-induced apoptosis has long-term male infertility effects.