ER Stress-induced Apoptosis Research Articles

The cytoplasmic-nuclear transport of DDX3X promotes immune-mediated liver injury in mice regulated by endoplasmic reticulum stress

Immune-mediated liver injury is a common characteristic of various liver diseases, including autoimmune and viral hepatitis. Here, we investigated the role of DEAD-box helicase 3, X-linked (DDX3X) in immune-mediated liver injury. Liver injury was induced in C57BL/6J mice via concanavalin A (Con A). DDX3X hepatocyte-specific knockout (DDX3XΔHep) mice and control (DDX3Xfl/fl) mice were utilized to investigate the role of DDX3X in liver injury. Primary hepatocytes were treated with tunicamycin (TM) to induce ER stress in vitro. The expression of DDX3X in patients with various liver diseases was evaluated. Hepatic DDX3X expression increased, and DDX3X translocated from the cytoplasm to the nucleus during Con A-induced liver injury. DDX3X deficiency ameliorated mouse liver injury and reduced ER stress in liver tissue. The inhibition of ER stress with 4-PBA significantly attenuated liver injury while decreasing DDX3X levels in liver tissue. However, the upregulation of hepatic DDX3X expression reversed Con A-induced liver injury and negated the protective effect of 4-PBA. Mechanistically, the nuclear translocation of DDX3X promoted ER stress-induced apoptosis through the transcriptional induction of CHOP. Moreover, DDX3X was elevated and translocated into the nucleus in patients with HBV-LF and AIH. Additionally, serum DDX3X levels markedly increased in patients with HBV-LF, and a consistent decrease in DDX3X was associated with a good prognosis. The cytoplasmic-to-nuclear translocation of DDX3X promotes ER stress-induced apoptosis, which is an obligatory step that drives hepatic necrosis and tissue damage. Notably, DDX3X is a potential therapeutic target for immune-mediated liver injury.

Megakaryocyte maturation involves activation of the adaptive unfolded protein response.

Endoplasmic reticulum stress triggers the unfolded protein response (UPR) to promote cell survival or apoptosis. Transient endoplasmic reticulum stress activation has been reported to trigger megakaryocyte production, and UPR activation has been reported as a feature of megakaryocytic cancers. However, the role of UPR signaling in megakaryocyte biology is not fully understood. We studied the involvement of UPR in human megakaryocytic differentiation using PMA (phorbol 12-myristate 13-acetate)-induced maturation of megakaryoblastic cell lines and thrombopoietin-induced differentiation of human peripheral blood-derived progenitors. Our results demonstrate that an adaptive UPR is a feature of megakaryocytic differentiation and that this response is not associated with ER stress-induced apoptosis. Differentiation did not alter the response to the canonical endoplasmic reticulum stressors DTT or thapsigargin. However, thapsigargin, but not DTT, inhibited differentiation, consistent with the involvement of Ca2+ signaling in megakaryocyte differentiation.

Melatonin inhibits tongue squamous cell carcinoma: Interplay of ER stress-induced apoptosis and autophagy with cell migration

Tongue squamous cell carcinoma (TSCC) occupies a high proportion of oral squamous cell carcinoma. TSCC features high lymph node metastasis rates and chemotherapy resistance with a poor prognosis. Therefore, an effective therapy strategy is needed to improve patient prognosis. Melatonin (MT) is a natural indole compound shown to have anti-tumor effects in several cancers. This study focused on the role and mechanism of MT in TSCC cells. The results of the study suggest that MT could inhibit cell proliferation in CRL-1623 cells. Western blot analysis showed the down-regulate of cyclin B1 and the up-regulate P21 protein by MT. MT was also shown to down-regulate the expression of Zeb1, Wnt5A/B, and β-catenin protein and up-regulate E-cadherin to inhibit the migration of CRL-1623 cells. MT also promoted the expression of ATF4, ATF6, Bip, BAP31 and CHOP in CRL-1623 cells leading to endoplasmic reticulum stress, and induced autophagy and apoptosis in CRL-1623 cells. Western blots showed that MT could promote the expression of Bax, LC3, and Beclin1 proteins and inhibit the expression of p62. We screened differentially expressed long non-coding RNAs (lncRNAs) in MT-treated cells and found that the expression of MALAT1 and H19 decreased. Moreover, MT inhibited tumor growth in nude mice inoculated with CRL-1623 cells. These results suggest that MT could induce autophagy, promote apoptosis, and provide a potential natural compound for the treatment of TSCC.

Glycyrrhetinic acid attenuates endoplasmic reticulum stress-induced hepatocyte apoptosis via CHOP/DR5/Caspase 8 pathway in cholestasis

Bile acid (BA)-induced apoptosis is a common pathologic feature of cholestatic liver injury. Glycyrrhetinic acid (GA) is the hepatoprotective constituent of licorice. In the present study, the anti-apoptotic potential of GA was investigated in wild type and macrophage-depleted C57BL/6 mice challenged with alpha-naphthyl isothiocyanate (ANIT), and hepatocytes stimulated with Taurocholic acid (TCA) or Tumor necrosis factor-alpha (TNF-α). Apoptosis was determined by TUNEL positive cells and expression of executioner caspases. Firstly, we found that GA markedly alleviated liver injury, accompanied with reduced positive TUNEL-staining cells, and expression of caspases 3, 8 and 9 in mice modeled with ANIT. Secondly, GA mitigated apoptosis in macrophage-depleted mice with exacerbated liver injury and augmented cell apoptosis. In vitro study, pre-treatment with GA reduced the expression of activated caspases 3 and 8 in hepatocytes stimulated with TCA, but not TNF-α. The ability of GA to ameliorate apoptosis was abolished in the presence of Tauroursodeoxycholic Acid (TUDCA), a chemical chaperon against Endoplasmic reticulum stress (ER stress). Furthermore, GA attenuated the over-expression of Glucose regulated protein 78 (GRP78), and blocked all three branches of Unfolded protein reaction (UPR) in cholestatic livers of mice induced by ANIT. GA also downregulated C/EBP homologous protein (CHOP) expression, accompanied with reduced expression of Death receptor 5 (DR5) and activation of caspase 8 in both ANIT-modeled mice and TCA-stimulated hepatocytes. The results indicate that GA inhibits ER stress-induced hepatocyte apoptosis in cholestasis, which correlates with blocking CHOP/DR5/Caspase 8 pathway.

Astragaloside IV protects cardiomyocytes from hypoxic injury by regulating endoplasmic reticulum stress via eIF2α/CHOP signaling pathway.

Endoplasmic reticulum stress (ER stress) is suggested to promote cardiomyocyte apoptosis and ultimately lead to ischemic injury. Inhibition of ER stress-induced apoptosis may be a therapeutic strategy for MI injury. Astragaloside-IV (AST) from Astragalus membranaceus (Fisch) Bge, was reported to have cardioprotective properties. In this study, we investigated the protective effect of AST on cardiomyocytes against hypoxia injury by regulating ER stress and inhibiting apoptosis. H9c2 cardiomyocytes were divided into three groups, normal group, hypoxia group and AST group. Cell viability was determined by CCK-8 assay. Intracellular reactive oxygen species (ROS) production was detected by DCFH-DA (2,7- dichloro-dihydrofluorescein diacetate) florescent staining. The study showed that AST treatment could significantly increase the cell viability of H9c2 cells exposed to hypoxia. Furthermore, AST could restrain cell apoptosis and decrease the production of ROS. Compared with normal group, the protein levels of Bax, caspase-3, caspase-9, GRP78, p-eIF2α, and CHOP were enhanced in the hypoxia group, whereas the protein level of Bcl-2 was dramatically reduced. Compared with hypoxia group, AST markedly inhibited the phosphorylation of eIF2α and the expression of caspase-3, caspase-9 and CHOP, and promoted the protein expression of Bcl-2. Thus, AST can inhibit the ER stress-mediated apoptosis, partly through the eIF2α/CHOP pathway suppression to inhibit ER stress.

Ajugol's upregulation of TFEB-mediated autophagy alleviates endoplasmic reticulum stress in chondrocytes and retards osteoarthritis progression in a mouse model

BackgroundOsteoarthritis (OA), a degenerative disease with a high global prevalence, is characterized by the degradation of the extracellular matrix (ECM) and the apoptosis of chondrocytes. Ajugol, a extract derived from the herb Rehmannia glutinosa, has not yet been investigated for its potential in modulating the development of OA.MethodsWe employed techniques such as western blotting, immunofluorescence, immunohistochemistry, X-ray imaging, HE staining, and SO staining to provide biological evidence supporting the role of Ajugol as a potential therapeutic agent for modulating OA. Furthermore, in an in vivo experiment, intra-peritoneal injection of 50 mg/kg Ajugol effectively mitigated the progression of OA following destabilization of the medial meniscus (DMM) surgery.ResultsOur findings revealed that treatment with 50 μM Ajugol activated TFEB-mediated autophagy, alleviating ER stress-induced chondrocyte apoptosis and ECM degradation caused by TBHP. Furthermore, in an in vivo experiment, intra-peritoneal injection of 50 mg/kg Ajugol effectively mitigated the progression of OA following destabilization of the medial meniscus (DMM) surgery.ConclusionThese results provide compelling biological evidence supporting the role of Ajugol as a potential therapeutic agent for modulating OA by activating autophagy and attenuating ER stress-induced cell death and ECM degradation. The promising in vivo results further suggest the potential of Ajugol as a treatment strategy for OA progression.

SEC23A confers ER stress resistance in gastric cancer by forming the ER stress-SEC23A-autophagy negative feedback loop

BackgroundSec23 homolog A (SEC23A), a core component of coat protein complex II (COPII), has been reported to be involved in several cancers. However, the role of SEC23A in gastric cancer remains unclear.MethodsThe expression of SEC23A in gastric cancer was analyzed by using qRT-PCR, western blotting and IHC staining. The role of SEC23A in ER stress resistance was explored by functional experiments in vitro and vivo. The occupation of STAT3 on the SEC23A promoter region was verified by luciferase reporter plasmids and CHIP assay. The interaction between SEC23A and ANXA2 was identified by Co-IP and mass spectrometry analysis.ResultsWe demonstrated that SEC23A was upregulated in gastric cancer and predicted poor prognosis in patients with gastric cancer. Mechanistically, SEC23A was transcriptional upregulated by ER stress-induced pY705-STAT3. Highly expressed SEC23A promoted autophagy by regulating the cellular localization of ANXA2. The SEC23A-ANXA2-autophay axis, in turn, protected gastric cancer cells from ER stress-induced apoptosis. Furthermore, we identified SEC23A attenuated 5-FU therapeutic effectiveness in gastric cancer cells through autophagy-mediated ER stress relief.ConclusionWe reveal an ER stress-SEC23A-autophagy negative feedback loop that enhances the ability of gastric cancer cells to resist the adverse survival environments. These results identify SEC23A as a promising molecular target for potential therapeutic intervention and prognostic prediction in patients with gastric cancer.

UPR-Induced miR-616 Inhibits Human Breast Cancer Cell Growth and Migration by Targeting c-MYC.

C/EBP homologous protein (CHOP), also known as growth arrest and DNA damage-inducible protein 153 (GADD153), belongs to the CCAAT/enhancer-binding protein (C/EBP) family. CHOP expression is induced by unfolded protein response (UPR), and sustained CHOP activation acts as a pivotal trigger for ER stress-induced apoptosis. MicroRNA-616 is located within an intron of the CHOP gene. However, the regulation of miR-616 expression during UPR and its function in breast cancer is not clearly understood. Here we show that the expression of miR-616 and CHOP (host gene of miR-616) is downregulated in human breast cancer. Both miR-5p/-3p arms of miR-616 are expressed with levels of the 5p arm higher than the 3p arm. During conditions of ER stress, the expression of miR-616-5p and miR-616-3p arms was concordantly increased primarily through the PERK pathway. Our results show that ectopic expression of miR-616 significantly suppressed cell proliferation and colony formation, whereas knockout of miR-616 increased it. We found that miR-616 represses c-MYC expression via binding sites located in its protein coding region. Furthermore, we show that miR-616 exerted growth inhibitory effects on cells by suppressing c-MYC expression. Our results establish a new role for the CHOP locus by providing evidence that miR-616 can inhibit cell proliferation by targeting c-MYC. In summary, our results suggest a dual function for the CHOP locus, where CHOP protein and miR-616 can cooperate to inhibit cancer progression.

LINP1 represses unfolded protein response by directly inhibiting eIF2α phosphorylation to promote cutaneous squamous cell carcinoma

BackgroundEndoplasmic reticulum stress (ER stress) may destroy endoplasmic reticulum homeostasis (ER homeostasis) and leads to programmable cell death. Unfolded protein response (UPR) originally stimulated by ER stress is critical for the survival of tumor cells through trying to re-establish ER homeostasis as an adaption to harsh microenvironment. However, mechanisms involving key regulators in modulating UPR remain underexplored.MethodsThe expression of LINP1 in cutaneous squamous cell carcinoma (cSCC) tissues and cell lines was assessed. Subsequently, LINP1 was knocked out, knocked down or overexpressed in cSCC cells. CCK-8 assays, colony forming assays, transwell migration assays and invasiveness measurement by matrigel-coated transwell were performed to examine the role of LINP1 in cSCC development through gain-of-function and loss-of-function experiments. Transcriptomic sequencing (RNA-Seq) was conducted and indicated the key downstream signaling events regulated by LINP1 including UPR and apoptosis signaling. Furthermore, the direct interaction between LINP1 and eIF2α to modulate UPR and apoptosis was confirmed by RNA pulldown, RNA immunoprecipitation (RIP), ChIP-qPCR and in vitro phosphorylation assays.ResultsIn this study, LncRNA in non-homologous end joining pathway 1 (LINP1) was identified to be one of the top ten highest-expressed LncRNAs in cSCC, the second most common cancer in the world. Functional studies using in vitro and in vivo models revealed that LINP1 functions as an oncogene to promote cell proliferation, colony formation, migration and invasiveness while inhibiting cell apoptosis in cSCC. Transcriptomic sequencing after knockdown of LINP1 indicated LINP1 negatively regulates UPR-related pathways involving key effectors for activating UPR and the apoptosis following the prolonged UPR. Mechanistic study showed LINP1 physically interacts with eIF2α to inhibit its phosphorylation for avoiding unmitigated UPR. Loss of LINP1 followed by enhanced eIF2α phosphorylation led to overactivated UPR and induced DDIT3 expression, contributing to ER stress-induced apoptosis and suppression of cSCC development.ConclusionsOur findings demonstrate a novel regulatory hierarchy of UPR by demonstrating LINP1 as a critical modulator for eIF2α phosphorylation and a suppressor of UPR-mediated apoptosis, which suggests a novel therapeutic target for cSCC treatment.

Activation of glucagon-like peptide-1 receptor in microglia exerts protective effects against sepsis-induced encephalopathy via attenuating endoplasmic reticulum stress-associated inflammation and apoptosis in a mouse model of sepsis

Sepsis-induced encephalopathy (SAE) is a detrimental complication in patients with severe sepsis, while there is still no effective treatment. Previous studies have elucidated the neuroprotective effects of glucagon-like peptide-1 receptor (GLP-1R) agonists. However, the role of GLP-1R agonists in the pathological process of SAE is unclear. Here, we found that GLP-1R was up-regulated in the microglia of septic mice. The activation of GLP-1R with Liraglutide could inhibit endoplasmic reticulum stress (ER stress) and associated inflammatory response as well as apoptosis triggered by LPS or tunicamycin (TM) in BV2 cells. In vivo experiments confirmed the benefits of Liraglutide in the regulation of microglial activation, ER stress, inflammation, and apoptosis in the hippocampus of septic mice. Additionally, the survival rate and cognitive dysfunction of septic mice were also improved after Liraglutide administration. Mechanically, cAMP/PKA/CREB signaling is involved in the protection of ER stress-induced inflammation and apoptosis in cultured microglial cells under LPS or TM stimulations. In conclusion, we speculated that GLP-1/GLP-1R activation in microglia might be a potential therapeutic target for the treatment of SAE.

EVA1A regulates hematopoietic stem cell regeneration via ER-mitochondria mediated apoptosis

Excessive protein synthesis upon enhanced cell proliferation frequently results in an increase of unfolded or misfolded proteins. During hematopoietic regeneration, to replenish the hematopoietic system, hematopoietic stem cells (HSCs) are activated and undergo a rapid proliferation. But how the activated HSCs respond to the proliferation pressure is still ambiguous; The proper control of the functional reservoir in the activated HSCs remains poorly understood. Here, we show a significant upregulation of EVA1A protein associated with the increase of ER stress during hematopoietic regeneration. Deletion of Eva1a significantly enhances the regeneration capacity of HSCs by inhibiting the ER stress-induced apoptosis. Mechanistically, the expression of EVA1A protein was upregulated by CHOP, and thereby promoted the ER-mitochondria interlinking via MCL1, which resulted in mitochondria-mediated apoptosis. These findings reveal a pathway for ER stress responses of HSCs by the EVA1A mediated apoptosis, which play an important role in HSCs regeneration.

LINC00629 protects osteosarcoma cell from ER stress-induced apoptosis and facilitates tumour progression by elevating KLF4 stability

BackgroundEscaping from ER stress-induced apoptosis plays an important role in the progression of many tumours. However, its molecular mechanism in osteosarcoma remains incompletely understood.MethodsThe molecular mechanism was investigated using RNA sequencing, qRT–PCR and Western blot assays. The relationship between LINC00629 and KLF4 was investigated using RNA pulldown and ubiquitylation assays. The transcriptional regulation of laminin subunit alpha 4 (LAMA4) by KLF4 was identified using bioinformatic analysis, a luciferase assay, and a chromatin immunoprecipitation assay.ResultsHere, we demonstrated that LINC00629 was increased under ER stress treatment. Elevated LINC00629 inhibited ER stress-induced osteosarcoma cell apoptosis and promoted clonogenicity and migration in vitro and in vivo. Further mechanistic studies indicated that LINC00629 interacted with KLF4 and suppressed its degradation, which led to a KLF4 increase in osteosarcoma. In addition, we also found that KLF4 upregulated LAMA4 expression by directly binding to its promoter and that LINC00629 inhibited ER stress-induced apoptosis and facilitated osteosarcoma cell clonogenicity and metastasis by activating the KLF4-LAMA4 pathway.ConclusionCollectively, our data indicate that LINC00629 is a critical long noncoding RNA (lncRNA) induced by ER stress and plays an oncogenic role in osteosarcoma cell by activating the KLF4-LAMA4 axis.

Loss-of-rescue of Ryr1I4895T-related pathology by the genetic inhibition of the ER stress response mediator CHOP

RYR1 is the gene encoding the ryanodine receptor 1, a calcium release channel of the endo/sarcoplasmic reticulum. I4898T in RYR1 is one of the most common mutations that give rise to central core disease (CCD), with a variable phenotype ranging from mild to severe myopathy to lethal early-onset core-rod myopathy. Mice with the corresponding I4895T mutation in Ryr1 present mild myopathy when the mutation is heterozygous while I4895T homozygous is perinatal-lethal. Here we show that skeletal muscles of I4895T homozygous mice at birth present signs of stress of the endoplasmic reticulum (ER stress) and of the related unfolded protein response (UPR) with increased levels of the maladaptive mediators CHOP and ERO1. To gain information on the role of CHOP in the pathogenesis of RYR1I4895T-related myopathy, we generated compound Ryr1I4895T, Chop knock-out (-/-) mice. However, the genetic deletion of Chop, although it attenuates ER stress in the skeletal muscle of the newborns, does not rescue any phenotypic or functional features of Ryr1I4895T in mice: neither the perinatal-lethal phenotype nor the inability of Ryr1I4895T to respond to its agonist caffeine, but protects from ER stress-induced apoptosis. These findings suggest that genetic deletion of the ER stress response mediator CHOP is not sufficient to counteract the pathological Ryr1I4895T phenotype.

Hcmv-miR-UL148D regulates the staurosporine-induced apoptosis by targeting the Endoplasmic Reticulum to Nucleus signaling 1(ERN1).

The propensity of viruses to co-opt host cellular machinery by reprogramming the host’s RNA-interference machinery has been a major focus of research, however, regulation of host defense mechanisms by virus-encoded miRNA, is an additional regulatory realm gaining momentum in the arena of host-viral interactions. The Human Cytomegalovirus (HCMV) miRNAs, regulate many cellular pathways alone or in concordance with HCMV proteins, thereby paving a conducive environment for successful infection in the human host. We show that HCMV miRNA, hcmv-miR-UL148D inhibits staurosporine-induced apoptosis in HEK293T cells. We establish that ERN1 mRNA is a bonafide target of hcmv-miR-UL148D and its encoded protein IRE1α is translationally repressed by the overexpression of hcmv-miR-UL148D resulting in the attenuation of apoptosis. Unlike the host microRNA seed sequence (6–8 nucleotides), hcmv-miR-UL148D has long complementarity to 3’ UTR of ERN1 mRNA resulting in mRNA degradation. The repression of IRE1α by the hcmv-miR-UL148D further downregulates Xbp1 splicing and c-Jun N-terminal kinase phosphorylation thus regulating ER-stress and ER-stress induced apoptotic pathways. Strikingly, depletion of ERN1 attenuates staurosporine-induced apoptosis which further suggests that hcmv-miR-UL148D functions through regulation of its target ERN1. These results uncover a role for hcmv-miR-UL148D and its target ERN1 in regulating ER stress-induced apoptosis.

Exercise and Metformin Intervention Prevents Lipotoxicity-Induced Hepatocyte Apoptosis by Alleviating Oxidative and ER Stress and Activating the AMPK/Nrf2/HO-1 Signaling Pathway in db/db Mice.

Objective Nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2DM) commonly coexist and act synergistically to drive adverse clinical outcomes. This study is aimed at investigating the effects of exercise intervention and oral hypoglycaemic drug of metformin (MET) alone or combined on hepatic lipid accumulation. To investigate if oxidative stress and endoplasmic reticulum stress (ERS) are involved in lipotoxicity-induced hepatocyte apoptosis in diabetic mice and whether exercise and/or MET alleviated oxidative stress or ERS-apoptosis by AMPK-Nrf2-HO-1 signaling pathway. Methods Forty db/db mice with diabetes (random blood glucose ≥ 250 mg/dL) were randomly allocated into four groups: control (CON), exercise training alone (EX), metformin treatment alone (MET), and exercise combined with metformin (EM) groups. Hematoxylin-eosin and oil red O staining were carried out to observe hepatic lipid accumulation. Immunohistochemical and TUNEL methods were used to detect the protein expression of the binding immunoglobulin protein (BiP) and superoxide dismutase-1 (SOD1) and the apoptosis level of hepatocytes. ERS-related gene expression and the AMPK-Nrf2-HO-1 signaling pathway were tested by western blotting. Results Our data showed that db/db mice exhibited increased liver lipid accumulation, which induced oxidative and ER stress of the PERK-eIF2α-ATF4 pathway, and hepatocyte apoptosis. MET combined with exercise training significantly alleviated hepatic lipid accumulation by suppressing BiP expression, the central regulator of ER homeostasis, and its downstream PERK-eIF2α-ATF4 pathway, as well as upregulated the AMPK-Nrf2-HO-1 signaling pathway. Moreover, the combination of exercise and MET displayed protective effects on hepatocyte apoptosis by downregulating Bax expression and TUNEL-positive staining, restoring the balance of cleaved-caspase-3 and caspase-3, and improving the antioxidant defense system to prevent oxidative damage in db/db mice. Conclusion Compared to MET or exercise intervention alone, the combined exercise and metformin exhibited significant effect on ameliorating hepatic steatosis, inhibiting oxidative and ER stress-induced hepatocyte apoptosis via improving the capacity of the antioxidant defense system and suppression of the PERK-eIF2α-ATF4 pathway. Furthermore, upregulation of AMPK-Nrf2-HO-1 signaling pathway might be a key crosstalk between MET and exercise, which may have additive effects on alleviating hepatic lipid accumulation.

Sphingosine-1-phosphate Attenuates Endoplasmic Reticulum Stress-induced Cardiomyocyte Apoptosis Through Sphingosine-1-phosphate Receptor 1

Endoplasmic reticulum stress (ER stress) is involved in the development and progression of various forms of heart disease and may lead to myocardial apoptosis. Sphingosine-1-phosphate (S1P) possesses cardioprotective properties, including anti-apoptosis. However, little is known about the link between S1P and ER stress-induced myocardial apoptosis. This study investigated the regulatory role of S1P in ER stress-induced apoptosis in cardiomyocytes. ER stress and myocardial apoptosis were induced by transverse aortic constriction (TAC) or tunicamycin in mice, which were then treated with 2-acetyl-5-tetrahydroxybutyl imidazole (THI) or S1P. AC16 cells were treated with tunicamycin or thapsigargin, or pretreated with S1P, sphingosine-1-phosphate receptor (S1PR) subtype antagonists, S1PR1 agonist, and PI3K and MEK inhibitors. Cardiac function, the level of S1P in plasma and heart, ER stress markers, cell viability, and apoptosis were detected. S1P reduced the expression of ER stress-related molecules and ER stress-induced myocardial apoptosis in mice subjected to TAC or an injection of tunicamycin. Furthermore, in AC16 cells exposed to thapsigargin or tunicamycin, S1P decreased the expression of ER stress-related molecules, promoting cell viability and survival. Nevertheless, the S1PR1 antagonist abrogated the protection of S1P. Subsequently, in TAC S1PR1 heterozygous (S1PR1^+/-) mice, S1P had no effect on ER stress and apoptosis in cardiomyocytes. Notably, in vitro, the impact of anti-ER stress-induced myocardial apoptosis by the S1PR1 agonist was reversed by PI3K and MEK inhibitors. This study is the first to demonstrate that S1P relieves ER stress-induced myocardial apoptosis via S1PR1/AKT and S1PR1/ERK1/2, which are potential therapeutic targets for heart disease.

Sorafenib combined with STAT3 knockdown triggers ER stress-induced HCC apoptosis and cGAS-STING-mediated anti-tumor immunity

Sorafenib is the first-line treatment for advanced hepatocellular carcinoma (HCC). However, it is difficult to alleviate this disease process using single-agent chemotherapy. Using combination therapies for advanced HCC has become a major trend. Given that STAT3 overexpression is involved in chemotherapy resistance and the immune escape of HCC cells, it has become a potential therapeutic target for HCC in recent years. GEO database analysis showed that STAT3 levels in tumor tissues from non-responders were significantly higher than those in responders to sorafenib. Our studies demonstrated that STAT3 knockdown promoted sorafenib-induced ER stress-induced apoptosis. Importantly, the DNA released by dead HCC cells stimulated the cGAS-STING signaling pathway in CD103+ DCs and promoted type I interferon production, thus, enhancing the anti-tumor function of CD8+ T and NK cells. In conclusion, our results revealed that the combination strategy of sorafenib and STAT3 knockdown might be a potential treatment strategy for HCC, directly and efficiently disturbing the tumor features of HCC cells while improving the tumor microenvironment via the cGAS-STING-Type I IFNs axis of DCs, inducing anti-HCC immune responses.

Rhomboid pseudoproteases: An Achilles heel's for BCL-2/IP3R-dependent resistance to ER stress-induced cell death

Anti-apoptotic BCL-2 targets and inhibits IP3 receptors (IP3Rs), thereby preventing apoptosis by limiting ER-mitochondrial Ca2+ flux. Recently, Dulloo et al. (2022), Nat. Comm. 13:1257[6] revealed a novel role for rhomboid pseudoproteases in ER stress-induced apoptosis by stripping BCL-2 from IP3Rs, thereby enabling pro-apoptotic Ca2+ signaling.

Deletion of Gdf15 Reduces ER Stress-induced Beta-cell Apoptosis and Diabetes.

Endoplasmic reticulum (ER) stress contributes to pancreatic beta-cell apoptosis in diabetes, but the factors involved are still not fully elucidated. Growth differentiation factor 15 (GDF15) is a stress response gene and has been reported to be increased and play an important role in various diseases. However, the role of GDF15 in beta cells in the context of ER stress and diabetes is still unclear. In this study, we have discovered that GDF15 promotes ER stress-induced beta-cell apoptosis and that downregulation of GDF15 has beneficial effects on beta-cell survival in diabetes. Specifically, we found that GDF15 is induced by ER stress in beta cells and human islets, and that the transcription factor C/EBPβ is involved in this process. Interestingly, ER stress-induced apoptosis was significantly reduced in INS-1 cells with Gdf15 knockdown and in isolated Gdf15 knockout mouse islets. In vivo, we found that Gdf15 deletion attenuates streptozotocin-induced diabetes by preserving beta cells and insulin levels. Moreover, deletion of Gdf15 significantly delayed diabetes development in spontaneous ER stress-prone Akita mice. Thus, our findings suggest that GDF15 contributes to ER stress-induced beta-cell apoptosis and that inhibition of GDF15 may represent a novel strategy to promote beta-cell survival and treat diabetes.

CARM1 promotes gastric cancer progression by regulating TFE3 mediated autophagy enhancement through the cytoplasmic AMPK-mTOR and nuclear AMPK-CARM1-TFE3 signaling pathways

BackgroundThe role of CARM1 in tumors is inconsistent. It acts as an oncogene in most cancers but it inhibits the progression of liver and pancreatic cancers. CARM1 has recently been reported to regulate autophagy, but this function is also context-dependent. However, the effect of CARM1 on gastric cancer (GC) has not been studied. We aimed to explore whether CARM1 was involved in the progression of GC by regulating autophagy.MethodsThe clinical values of CARM1 and autophagy in GC were evaluated by immunohistochemistry and qRT–PCR. Transmission electron microscopy, immunofluorescence and western blotting were employed to identify autophagy. The role of CARM1 in GC was investigated by CCK-8, colony formation and flow cytometry assays in vitro and a xenograft model in vivo. Immunoprecipitation assays were performed to determine the interaction of CARM1 and TFE3.ResultsCARM1 was upregulated in clinical GC tissues and cell lines, and higher CARM1 expression predicted worse prognosis. CARM1 enhanced GC cell proliferation, facilitated G1-S transition and inhibited ER stress-induced apoptosis by regulating autophagy. Importantly, treatment with a CARM1 inhibitor rescued the tumor-promoting effects of CARM1 both in vitro and in vivo. Furthermore, we demonstrated that CARM1 promoted TFE3 nuclear translocation to induce autophagy through the cytoplasmic AMPK-mTOR and nuclear AMPK-CARM1-TFE3 signaling pathways.ConclusionCARM1 promoted GC cell proliferation, accelerated G1-S transition and reduced ER stress-induced apoptosis by regulating autophagy. Mechanistically, CARM1 triggered autophagy by facilitating TFE3 nuclear translocation through the AMPK-mTOR and AMPK-CARM1-TFE3 signaling pathways.