Glucose-regulated Protein Research Articles

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

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

Characterization and function analysis of a glucose-regulated protein 78 gene in Neocaridina denticulata sinensis

Characterization and function analysis of a glucose-regulated protein 78 gene in Neocaridina denticulata sinensis

Alterations in Autophagic Function and Endoplasmic Reticulum Stress Markers in the Peripheral Blood Mononuclear Cells of Patients on Hemodialysis.

Oxidative stress, endoplasmic reticulum (ER) stress, and alterations in autophagy activity have been described as prominent factors mediating many pathological processes in chronic kidney disease (CKD). The accumulation of misfolded proteins in the ER may stimulate the unfolded protein response (UPR). The interplay between autophagy and UPR in hemodialysis (HD) patients remains unclear. The aim of the present study was to explore the associations between serum oxidative stress markers, autophagy activity, and ER stress markers in the peripheral blood mononuclear cells (PBMCs) of patients on HD. Autophagy and ER stress-related protein expression levels in PBMCs were measured using western blotting. The redox state of human serum albumin was measured via high-performance liquid chromatography. Levels of the microtubule associated protein light chain 3 (LC3)-II, BECLIN1, and p62/SQSTM1 proteins were significantly increased in PBMCs of HD patients compared to healthy subjects. The PBMCs in HD patients also displayed augmented glucose-regulated protein 78 kDa (GRP78), phosphorylated eukaryotic translation initiation factor 2, subunit 1 alpha (p-eIF2α), and activating transcription factor 6 (ATF6) levels (p < 0.05). Additionally, nuclear factor erythroid 2 (NF-E2)-related factor 2 (NRF2) levels were elevated in the PBMCs of HD patients, compared to those of healthy subjects. Correlation analysis showed that the redox status of albumin was significantly correlated with the p62 protein level in PBMCs. Compared to healthy controls, we found elevated autophagosome formation in HD patients. Increased expression of ER stress markers was also observed in HD patients. Furthermore, increased p62 expression was positively correlated with the protein expression of NRF2, as well as a reduced form of serum albumin (human mercaptalbumin; HMA), in HD patients.

L-3-n-butylphthalide alleviates intermittent alcohol exposure-induced hypothalamic cell apoptosis via inhibiting the IRE1α-ASK1-JNK pathway in adolescent rats.

Exposure to alcohol can induce different degrees of damage to various tissues and organs, and brain is the most vulnerable part affected by alcohol. However, there is no detailed report on whether intermittent alcohol exposure can result in pathological changes in the hypothalamus of adolescent rats and the detailed mechanism. This study investigated pathological changes in the hypothalamus, probed the levels of inflammatory factors, and detected the expression of proteins related to endoplasmic reticulum stress (ERS) to determine whether ERS is involved in the injury process of the hypothalamus and the protective mechanism of L-3-n-butylphthalide (L-NBP). The results showed that intermittent alcohol exposure induced hypothalamic nerve injury, including cell apoptosis, increased the levels of inflammatory factors, and upregulated the expression of glucose-regulated protein 78 (GRP78), p-Inositol Requiring Enzyme 1α (p-IRE1α), apoptosis signal-regulating kinase 1 (ASK1), and p-c-Jun N-terminal kinase (p-JNK)). Tauroursodeoxycholic acid (TUDCA), an ERS inhibitor, significantly reduced the pathological damage described above. The increases in the levels of inflammatory factors, pathological injury, and increased levels of proteins associated with the IRE1α-ASK1-JNK pathway were alleviated by L-NBP. The present study indicated that intermittent alcohol exposure could lead to hypothalamic cell apoptosis in adolescent rats and L-NBP could alleviate the above injury by inhibiting the IRE1α-ASK1-JNK pathway. Abbreviations: Ang-2, Angiopoietin-2; ASK1, Apoptosis signal-regulating kinase 1; ER, Endoplasmic reticulum; ERS, Endoplasmic reticulum stress; ELISA, Enzyme-linked immunosorbent assay; GFAP, Glial fibrillary acidic protein; GRP78, Glucose-regulated protein 78; IBA1, Ionized calcium binding adapter molecule 1; i.p., Intraperitoneal; IRE1α, Inositol Requiring Enzyme 1α; JNK, c-Jun N-terminal kinase; L-NBP, L-3-n-butylphthalide; PND, Postnatal day; PVDF, Polyvinylidene difluoride; SDS-PAGE, Sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TRAF2, TNF-receptor associated factor 2; TUDCA, Tauroursodeoxycholic acid; VEGF, Vascular endothelial growth factor.

Comprehensive analysis of the xbp1 gene in Pacific abalone Haliotis discus hannai: Structure, expression, and role in heat stress response.

The present study explores the x-box binding protein 1 (xbp1) gene in Haliotis discus hannai (Pacific abalone), focusing on its structure, expression, and functional role under heat stress. Southern blot revealed two copies of xbp1 in the intestine and mantle, one in the gill and muscle, and no detection in the digestive gland. mRNA expression levels were highest in the gill, followed by the mantle, intestine, and muscle, with the digestive gland showing the lowest expression. Actinomycin D treatment demonstrated that xbp1 mRNA stability varied among tissues, with slower degradation in the gill and mantle, while rapid degradation was observed in the digestive gland. Heat stress caused a 20 bp fragment removal from xbp1 mRNA, producing spliced xbp1 (xbp1s), with a conserved inositol-requiring enzyme 1α (IRE1α) cleavage motif (5'-CAGCACCUGCUGAUCCUCUG-3'). Genome walking was used to obtain the promoter sequences of downstream genes regulated by xbp1s. Through sequence conservation analysis, the binding sites of xbp1s on these promoters were identified in Pacific abalone. Yeast one-hybrid (Y1H) assays confirmed xbp1s binding to these sites, and morpholino oligonucleotides (MO) treatment effectively suppressed xbp1s production. Western blot analysis demonstrated that heat stress induced the expression of HDEL-related proteins, while MO injection significantly reduced their expression under both basal and heat stress conditions. Immunofluorescence analysis revealed decreased endoplasmic reticulum (ER) chaperone glucose-regulated protein 78 (GRP78) levels and increased apoptosis in MO-treated abalone under heat stress, suggesting a compromised ER stress response. These findings underscore XBP1's crucial role in regulating ER stress management and apoptotic processes, providing new insights into the functional significance of xbp1 in abalone's response to thermal stress.

MMP-2 inhibition attenuates ER stress-mediated cell death during myocardial ischemia-reperfusion injury by preserving IRE1α

Endoplasmic reticulum (ER) stress is one of the major events accompanying myocardial ischemia-reperfusion (IR) injury, as hypoxia and oxidative stress disrupt protein folding in the ER. As a result, the unfolded protein response (UPR) is activated through different sensors including inositol-requiring enzyme 1α (IRE1α) and protein kinase R-like ER kinase (PERK). Failure of the UPR to reduce ER stress induces cellular dysfunction. Matrix metalloproteinase-2 (MMP-2) is a ubiquitous protease that is activated intracellularly in response to oxidative stress and partially localizes near the ER. However, its role in ER homeostasis is unknown. We hypothesized that MMP-2 is involved in the regulation of the UPR and ER stress-mediated apoptosis during IR injury. Isolated mouse hearts subjected to IR injury showed impaired recovery of post-ischemic contractile function compared to aerobically perfused controls. Ventricular extracts from IR hearts had higher levels of glucose-regulated protein-78 and protein disulfide isomerase and lower levels of IRE1α and PERK compared to aerobic controls. MMP-2 inhibitors, ARP-100 or ONO-4817, given 10 min before ischemia, improved cardiac post-ischemic recovery and preserved IRE1α level in hearts subjected to 30 min ischemia/40 min reperfusion. IR also increased the levels of CHOP and mitochondrial Bax and caspase-3 and -9 activities, indicating induction of apoptosis, all of which were attenuated by MMP-2 inhibitors, regardless of the reperfusion time. Immunoprecipitation showed an association between MMP-2 and IRE1α in aerobic and IR hearts. During myocardial IR injury MMP-2 may impair the UPR and induce apoptosis by proteolysis of IRE1α. Inhibition of MMP-2 activity protects against cardiac contractile dysfunction in part by preserving IRE1α and preventing the progression to myocardial cell death.

Alpha-1 Antitrypsin Inclusions Sequester GRP78 in a Bile Acid-Inducible Manner.

The homozygous PiZ mutation (PIZZ genotype) constitutes the predominant cause of severe alpha-1 antitrypsin (AAT) deficiency and leads to liver disease via hepatocellular AAT aggregation. We systematically analysed the composition of AAT aggregates and studied the impact of bile acids. AAT inclusions were isolated from livers of PiZ overexpressing mice and PIZZ humans via fluorescence-activated and immunomagnetic sorting (FACS/MACS), while insoluble proteins were obtained via Triton-X extraction. Inclusion composition was evaluated through mass-spectrometry (MS), immunoblotting and immunostaining. Hepatocytes with versus without AAT aggregates were obtained via microdissection. Serum bile acids were assessed in 57 PIZZ subjects and 19 controls. Mice were administered 2% cholic acid (CA)-supplemented chow for 7 days. MS identified the key endoplasmic reticulum chaperone 78 kDa glucose-regulated protein (GRP78) in FACS/MACS pulldowns. GRP78 was also enriched in insoluble fractions from PiZ mice versus wild types and detected in insoluble fractions/MACS isolates from PIZZ liver explants. In cultured cells/primary hepatocytes, PiZ overexpression was associated with increased GRP78 mRNA/protein levels. In human livers, hepatocytes with AAT aggregates had higher GRP78 levels than hepatocytes without. PIZZ subjects displayed higher serum bile acid levels than controls and the highest levels were seen in individuals with liver injury/fibrosis. In PiZ mice, CA-mediated bile acid challenge resulted in increased liver injury and translocation of GRP78 into the aggregates. Our results demonstrate that GRP78 is sequestered within AAT inclusions. Bile acid accumulation, as seen in PIZZ subjects with liver disease, may promote GRP78 segregation and thereby augment liver damage. NCT02929940.

P-Coumaric Acid alleviates non-alcoholic fatty liver disease by promoting GLP-1 secretion via the GRP78-Ca2+ signaling axis

In individuals with obesity-related non-alcoholic fatty liver disease (NAFLD), endogenous Glucagon-like peptide-1 (GLP-1) secretion is compromised, and supplementation with GLP-1 receptor agonists has shown efficacy in ameliorating NAFLD. However, there is currently a scarcity of research focused on the direct promotion of endogenous GLP-1 secretion from L-cells by plant-derived phenolic acids. Hence, this study reveals that p-Coumaric Acid (p-CA), a widely occurring phenolic acid in the plant, holds potential as a therapeutic approach by stimulating the secretion of GLP-1 to improve glucose-lipid metabolism alterations and alleviate NAFLD symptoms. In diet-induced obese (DIO) mouse models, administration of high doses of p-CA led to a significant elevation in serum GLP-1 levels, as well as improvements in body weight gain, glucose level, insufficient insulin secretion, and biochemical abnormalities associated with NAFLD in mice fed with a high-fat diet. Moreover, the number of lipid droplets in the liver tissue of p-CA-treated mice was notably reduced, suggesting its effectiveness in mitigating liver fat accumulation and ameliorating NAFLD severity. Experimental evidence suggests that p-CA exerts its effects by influencing the transcriptional regulation of Glucose-regulated protein 78 kDa (GRP78) through interaction with Nucleophosmin 1 (NPM1), thereby downregulating GRP78 expression. This decrease in GRP78 expression subsequently leads to an increase in intracellular Calcium ions (Ca2+) concentration, which promotes the production and exocytosis of GLP-1-containing vesicles in L cells, consequently enhancing GLP-1 secretion. This research demonstrates the mechanistic role and therapeutic effects of p-CA in regulating GLP-1 secretion and its implications for improving NAFLD, underscoring the pharmacological significance of this natural compound as a dietary supplement.

β-Hydroxybutyrate Alleviates Atherosclerotic Calcification by Inhibiting Endoplasmic Reticulum Stress-Mediated Apoptosis via AMPK/Nrf2 Pathway.

Atherosclerotic calcification (AC) is a common feature of atherosclerotic cardiovascular disease. β-Hydroxybutyrate (BHB) has been identified as a molecule that influences cardiovascular disease. However, whether BHB can influence AC is still unknown. In this study, ApoE-/- mice, fed a Western diet, were used to examine the effects of BHB on AC. Rat vascular smooth muscle cells (VSMCs) were used to verify the impacts of BHB on AC and to explore the underlying mechanisms. The results show that Western diet-challenged ApoE-/- mice, supplemented with BHB for 24 weeks, exhibited reduced calcified areas, calcium content, and alkaline phosphatase (ALP) activity in the aortas, as well as ameliorated severity of AC. Furthermore, BHB downregulated the expression of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP), thereby reducing endoplasmic reticulum stress (ERS) and ERS-mediated apoptosis in the aortas of the mice. Consistently, in vitro studies showed that BHB reduced ALP activity and calcium content in VSMCs, and inhibited VSMC calcification. Additionally, BHB suppressed ERS-mediated apoptosis in VSMCs. In summary, the present results demonstrate that BHB can alleviate atherosclerotic calcification by inhibiting ERS-mediated apoptosis. Therefore, BHB may serve as a viable therapeutic agent for AC.

Possible Involvement of X-Box Binding Protein-1 in the Onset of Pulpitis.

Endoplasmic reticulum (ER) stress plays important roles not only in stress avoidance, but also in cell differentiation and maturation, cell proliferation, and promotion of bone formation. This study aimed to investigate the involvement of ER stress in the onset of pulpitis. Immunohistochemical analysis was conducted on human teeth extracted for orthodontic reasons. The effects of tunicamycin (TM), an inducer of ER stress, lipopolysaccharide (LPS), and 4μ8c, an inhibitor of inositol-requiring enzyme 1 (IRE1) on cultured human dental pulp cells (hDPCs) were also examined. The expressions of two ER stress markers, X-box binding protein (XBP)-1 and binding immunoglobulin protein (BiP)/78 kDa glucose-regulated protein (GRP78), were found in the human pulp tissues of a decayed tooth that had not developed irreversible acute pulpitis, but not in an impacted tooth without inflammation in pulp tissue. Both TM and LPS increased the mRNA levels of XBP-1, interleukin (IL)-6, and IL-8, whereas TM, but not LPS, enhanced the mRNA expression of BiP/GRP78 in hDPCs. 4μ8c significantly suppressed the increased level of XBP-1 by LPS. This study is the first to demonstrate that XBP-1, in addition to inflammatory cytokines, may participate in the onset of pulpitis through IRE1. These findings provide a more comprehensive understanding of pulpitis pathogenesis through the cooperation of ER stress and inflammatory cytokines.

Glucose-regulated protein 78 regulates the subunit-folding of the CCT complex by modulating gene expression and protein interaction in the microsporidian Nosema bombycis.

Chaperonin containing tailless complex polypeptide 1 (CCT) functions as a molecular chaperone and is essential for ensuring proper protein folding. Glucose-regulated protein 78 (GRP78/Bip), also a type of chaperone, not only assists in folding of proteins, but also facilitates the transportation of proteins into the endoplasmic reticulum (ER) via the Sec protein complex. In this study, we identified the CCTη of N. bombycis (NbCCTη) for the first time. Immunoprecipitations and mass spectrometry (IP-MS) of NbCCTη analysis showed that NbBip may interact with CCT subunits. Yeast two-hybrid assays validated that NbBip interacts with NbCCTη, as well as NbCCTα and NbCCTε. Furthermore, RNA interference on NbBip brought about radical expression of NbCCTα, NbCCTε, and NbCCTη, while RNAi on NbCCT subunits resulted in abnormal expression of NbBip. Immunofluorescence assay results showed that NbBip colocalized with NbCCTα and NbCCTη, and CCTη colocalized with Nbβ-tubulin and Nbactin in the parasite. Collectively, these findings suggest that NbBip may act as a crucial factor in the subunit-folding and assembly of CCT complex in N. bombycis.

Effect of 2,5-hexanedione on rat ovarian granulosa cell apoptosis involves endoplasmic reticulum stress-dependent m-TOR signaling pathway

ABSTRACT Occupational exposure to N-hexane/2,5-hexanedione (2,5-HD) was found to adversely affect reproductive functions in females. However, there are few studies regarding the mechanisms underlying reproductive system damage initiated by 2,5-HD. Several studies demonstrated that 2,5-HD exerts hormonal dysfunctions in females by promoting apoptosis using rat ovarian granulosa cells (GCs) as a model. The endoplasmic reticulum (ER) plays a key role in cellular processes such as protein folding and modification, Ca2+ storage, and lipid synthesis, which are known to involve the activation of stress (ERS)-dependent m-TOR signaling pathway. Thus, the aim of this study was to examine the effects of 2,5-HD on ER and the associated activation of stress (ERS)-dependent m-TOR signaling pathway resulting in consequent apoptosis of ovarian GCs. Data demonstrated that after intraperitoneal treatment with 100, 200, or 400 mg/kg 2,5-HD for 6 consecutive weeks, 5 times per week, a decrease in body weight, ovarian weight, and relative ovary weight was found. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay showed that 2,5-HD promoted apoptosis of ovarian GCs, which involved enhanced relative protein expression levels of m-TOR/p-mTOR. Our findings demonstrated that 2,5-HD (1) elevated expression levels of pro-apoptosis-related genes Bax and Caspase 3, (2) decreased expression levels of the anti-apoptosis gene Bcl-2, and (3) activated the protein expression of glucose-regulatory protein 78 (GRP78), inositol-requiring enzyme-1 (IRE1), and c-Jun terminal kinase (JNK) associated with increased apoptosis. Evidence indicates that chronic exposure to 2,5-HD induced apoptosis of ovarian GCs, and the possible mechanism underlying this effect involves the ERS-dependent m-TOR signaling pathway.

Characterization and Inhibition of the Chaperone Function of Plasmodium falciparum Glucose-Regulated Protein 94 kDa (PfGrp94).

Plasmodium falciparum expresses four heat shock protein 90 (Hsp90) members. Among these, one, glucose-regulated protein 94 (PfGrp94), is localized in the endoplasmic reticulum (ER). Both the cytosolic and ER-based Hsp90s are essential for parasite survival under all growth conditions. The cytosolic version has been extensively studied and has been targeted in several efforts through the repurposing of anticancer therapeutics as antimalarial drugs. However, PfGrp94 has not been fully characterized and some of its functions related to the ER stress response are not fully understood. Structural analysis of the recombinant full-length PfGrp94 protein showed a predominantly α-helical secondary structure and its thermal resilience was modulated by 5'-N-ethyl-carboxamide-adenosine (NECA) and nucleotides ATP/ADP. PfGrp94 exhibits ATPase activity and suppressed heat-induced aggregation of a model substrate, malate dehydrogenase, in a nucleotide-dependent manner. However, these PfGrp94 chaperone functions were abrogated by NECA. Molecular docking and molecular dynamics (MD) simulations showed that NECA interacted with unique residues on PfGrp94, which could be potentially exploited for selective drug design. Finally, using parasites maintained at the red blood stage, NECA exhibited moderate antiplasmodial activity (IC50 of 4.3, 7.4, and 10.0 μM) against three different P. falciparum strains. Findings from this study provide the first direct evidence for the correlation between in silico, biochemical, and invitro data toward utilizing the ER-based chaperone, PfGrp94, as a drug target against the malaria parasites.

Caralluma fimbriata Extract Improves Vascular Dysfunction in Obese Mice Fed a High-Fat Diet.

Obesity is a risk factor for developing cardiovascular diseases (CVDs) by impairing normal vascular function. Natural products are gaining momentum in the clinical setting due to their high efficacy and low toxicity. Caralluma fimbriata extract (CFE) has been shown to control appetite and promote weight loss; however, its effect on vascular function remains poorly understood. This study aimed to determine the effect that CFE had on weight loss and vascular function in mice fed a high-fat diet (HFD) to induce obesity, comparing this effect to that of lorcaserin (LOR) (an anti-obesity pharmaceutical) treatment. C57BL/6J male mice (n = 80) were fed a 16-week HFD to induce obesity prior to being treated with CFE and LOR as standalone treatments or in conjunction. Body composition data, such as weight gain and fat mass content were measured, isometric tension analyses were performed on isolated abdominal aortic rings to determine relaxation responses to acetylcholine, and immunohistochemistry studies were utilized to determine the expression profiles on endothelial nitric oxide synthase (eNOS) and cell stress markers (nitrotyrosine (NT) and 78 kDa glucose-regulated protein (GRP78)) in the endothelial, medial and adventitial layers of aortic rings. The results demonstrated that CFE and CFE + LOR treatments significantly reduced weight gain (17%; 24%) and fat mass deposition (14%; 16%). A HFD markedly reduced acetylcholine-mediated relaxation (p < 0.05, p < 0.0001) and eNOS expression (p < 0.0001, p < 0.01) and significantly increased NT (p < 0.05, p < 0.0001) and GRP78 (p < 0.05, p < 0.01, p < 0.001). Obese mice treated with CFE exhibited significantly improved ACh-induced relaxation responses, increased eNOS (p < 0.05, p < 0.01) and reduced NT (p < 0.01) and GRP78 (p < 0.05, p < 0.01) expression. Thus, CFE alone or in combination with LOR could serve as an alternative strategy for preventing obesity-related cardiovascular diseases.

Hypoxia Induced Lnc191 Upregulation Dictates the Progression of Esophageal Squamous Cell Carcinoma by Activating GRP78/ERK Pathway.

Hypoxia is a typical hallmark of solid tumors and plays a crucial role in the progression of esophageal squamous cell carcinogenesis (ESCC). Nevertheless, the precise mechanisms underlying the involvement of hypoxia in tumor development remain unclear. In the present study, a novel hypoxia-induced long noncoding RNA (lncRNA) is identified first, lnc191, which is highly expressed in clinical ESCC tissues and is positively correlated with poor prognosis of ESCC patients. These findings provide evidence that the hypoxia-inducible factor-1α (HIF-1α)-mediated transcriptional activation of lnc191 enhances the growth and metastasis of ESCC cells both in vitro and in vivo. Mechanistically, lnc191 interacts with GRP78 (78-kDa glucose-regulated protein), one of the endoplasmic reticulum chaperone proteins, leading to its translocation to the membrane, where GRP78 binds with EGFR and enhances its phosphorylation (Y845), further activates ERK/MAPK signaling pathway, and thereby in favor of the progression of ESCC. Overall, this data proposes lnc191 as a key driver during the development of ESCC and reveals the participation of the activated GRP78/ERK/MAPK axis in the ESCC progression mediated by lnc191. These findings indicate the potential of lnc191 as a promising diagnostic biomarker and therapeutic target in ESCC.

Taurine Protects Irinotecan-induced Muscle Dysfunction by Modulating Oxidative Stress and Endoplasmic Reticulum Stress in Human Skeletal Muscle Cells.

Irinotecan is a key component of standard first-line treatment for metastatic colorectal cancer. However, irinotecan-induced muscle dysfunction is a contributing factor to cancer cachexia. Here, we present the protective effect of taurine, a conditionally essential amino acid with great antioxidant properties, in attenuating muscle dysfunction induced by irinotecan. Irinotecan (20 μg/ml) was added to human skeletal muscle cells (HSkMCs) with or without pre-treatment of taurine (5 mM). The effects of taurine and irinotecan on the viability, cytotoxicity, and differentiation ability of HSkMC myoblasts were examined. The intracellular reactive oxygen species (ROS) and endoplasmic reticulum stress (ERS) were also monitored. Irinotecan caused cytotoxicity of HSkMCs, while taurine pretreatment increased cell viability and inhibited adenylate kinase release significantly in both myoblasts and myotubes. During differentiation, taurine increased ROS clearance and preserved the myotube differentiation ability impaired by irinotecan. Irinotecan exposure resulted in the up-regulation of CCAAT/enhancer-binding protein homologous protein (CHOP) and glucose-regulated protein 78 (GRP78). Taurine pretreatment could combat such irinotecan-induced ERS. The current in vitro study provides molecular evidence that taurine plays a beneficial role in protecting against irinotecan-induced muscle dysfunction by modulating oxidative stress and endoplasmic reticulum stress.

Serine protease inhibitor AEBSF(4-(2-aminoethyl)-benzenesulfonyl fluoride) decreased ischemic brain injury through inhibiting endoplasmic reticulum stress, oxidative stress, and autophagy in rats

4-(2-Aminoethyl)-benzenesulfonyl fluoride (AEBSF) is a serine protease inhibitor that may alleviate endoplasmic reticulum (ER) stress, a significant contributing factor to cerebral ischemia/reperfusion injury. The molecular crosstalk between ER stress, oxidative stress and autophagy represents a vicious cycle that can be pharmacologically targeted to minimize neuronal death after acute injuries to the central nervous system. However, the neuroprotective effects of AEBSF in the context of cerebral ischemia/reperfusion injury remain unknown. In this study,we reported the neuroprotective effect of AEBSF against cerebral ischemia/reperfusion injury and explored the mechanisms involved, particularly its role in reducing ER stress, oxidative stress and autophagy. Rats were pretreated with AEBSF or a vehicle before a 90-minute middle cerebral artery occlusion (MCAO) followed by 24 h of reperfusion. Our results demonstrate that AEBSF treatment reduced infarct volume and improved neurological function compared to vehicle treated rats after 24 h of reperfusion. Furthermore,AEBSF treatment decreased the expression of caspase-3, suggesting a decrease in neuronal apoptosis. Additionally, AEBSF treatment lowered levels of key ER stress biomarkers, including glucose-regulated protein 78 (GRP78), phosphorylated eukaryotic initiation factor 2α (p-eIF2α), and CCAAT-enhancer-binding protein homologous protein (CHOP), while the levels of inositol-requiring enzyme 1α (IRE1α) remained unchanged. AEBSF also decreased the oxidative stress biomarker neuronal nitric oxide synthase (nNOS) and its related molecule pro-MMP-9. Importantly, treatment with AEBSF reversed the trends of autophagy biomarker LC3B II/α-tubulin, Beclin1, and SQSTM1 at 24 h after reperfusion. In conclusion, AEBSF significantly mitigates ischemic brain damage and promotes neurological recovery by inhibiting ER stress, oxidative stress, and autophagy, highlighting its potential as a therapeutic option for ischemic stroke.

Guilu Erxian glue reduces endoplasmic reticulum stress-mediated apoptosis and restores the balance of extracellular matrix synthesis and degradation in chondrocytes by inhibiting the ATF6/GRP78/CHOP signaling pathway

Knee Osteoarthritis (KOA) is characterized by phenotypic alterations, apoptosis, and the breakdown of the extracellular matrix (ECM) in the superficial articular cartilage cells. The inflammatory response activates the Endoplasmic Reticulum Stress (ERS) signaling pathway, which plays a critical role in the pathophysiology and progression of KOA. Chondrocytes stimulated by thapsigargin(TG)exhibit heightened ERS and significantly increase the expression of ERS-associated proteins. Key mediators of ERS-induced apoptosis include X-box-binding protein 1(XBP1), elevated levels of the protein transport protein Sec61 subunit (SEC61), and C/EBP homologous protein (CHOP).While the precise mechanism of action of Guilu Erxian Glue (GEG), a medication commonly used in the clinical treatment of KOA, remains to be fully elucidated, our research has shown that GEG mitigates the imbalance between ECM synthesis and degradation, as well as chondrocyte apoptosis resulting from ERS. This effect is likely achieved through the suppression of the Activating Transcription Factor 6 (ATF6)/Glucose-Regulatory Protein 78 (GRP78)/CHOP signaling pathway.In summary,our research results indicate that GEG can activate the ATF6/GRP78/CHOP signaling pathway to restore endoplasmic reticulum (ER) homeostasis in chondrocytes, thereby reducing chondrocyte apoptosis and ultimately promoting the balance between ECM synthesis and degradation.

Function of PxGrp78 in the Reproduction of Plutella xylostella.

Glucose-regulated protein 78 (Grp78), a crucial molecular chaperone in the endoplasmic reticulum, has been extensively investigated in vertebrates. However, its functional exploration in insects remains limited. This study cloned the full-length cDNA sequence of Grp78 in Plutella xylostella (L.), which is 2583 bp long. The open reading frame (ORF) is 2004 bp in length and encodes a total of 667 amino acids, including three conserved characteristic sequences of the HSP70 family. PxGrp78 is expressed in various developmental stages of P. xylostella, with the highest expression observed in third instar larvae and higher expression in female adults compared to male adults. The interference with PxGrp78 in female adults was found to significantly reduce the quantity of egg laying and the hatching rate, as well as shorten the oviposition period and down-regulate the expression of the PxVg gene. These results suggested an important role for PxGrp78 in the reproduction of P. xylostella.

Sinapic acid alleviates glutamate-induced excitotoxicity by inhibiting neuroinflammation and endoplasmic reticulum stress pathway in C6 glioma cells

Sinapic acid (SA) is a polyphenol compound derived from hydroxycinnamic acid found in various foods such as cereals and vegetables and has antioxidant, anti-inflammatory and neuroprotective properties. However, its effects on glutamate-induced excitotoxicity, which is important in neurodegenerative diseases, have not been fully elucidated. This study aimed to investigate the effect of SA on glutamate excitotoxicity and the possible role of proinflammatory cytokines and the endoplasmic reticulum (ER) stress pathway. In the study, C6 rat glioma cell line was used and the cells were divided into 4 groups: control, glutamate, SA and glutamate+SA. Cells were treated with 10 mM glutamate for 24 h to induce excitotoxicity. Additionally, SA was applied to cells at concentrations of 12.5 to 100 μM to examine its effects on glutamate excitotoxicity. XTT test was used for cell viability, and apoptotic cells were determined by immunofluorescence and flow cytometry methods. Proinflammatory cytokines (tumor necrosis factor-alpha, TNF-α and interleukin-beta, IL-1β), ER stress markers (glucose regulatory protein 78, GRP78; C/EBP homologous protein, CHOP and activating transcription factor-4, ATF-4) and caspase-3 was used to measure ELISA method. Findings indicated that SA (50 μM) significantly increased cell viability against glutamate-induced excitotoxicity (p < 0.05). Also, SA caused a significant decrease in TNF-α, IL-1β, GRP78, CHOP, ATF-4 and caspase-3 levels in glutamate-treated cells (p < 0.05). Flow cytometry and immunofluorescence staining results showed that SA reduced apoptosis in C6 glioma cells. In conclusion, our findings suggested that SA attenuated glutamate-induced excitotoxicity by preventing apoptosis through reducing proinflammatory cytokines and ER stress protein levels.