The roles and mechanisms of endoplasmic reticulum stress-mediated autophagy in animal viral infections.

The endoplasmic reticulum (ER) is a unique organelle responsible for protein synthesis and processing, lipid synthesis in eukaryotic cells, and the replication of many animal viruses is closely related to ER. A considerable number of viral proteins are synthesised during viral infection, resulting in the accumulation of unfolded and misfolded proteins in ER, which in turn induces endoplasmic reticulum stress (ERS). ERS further drives three signalling pathways (PERK, IRE1, and ATF6) of the cellular unfolded protein response (UPR) to respond to the ERS. In numerous studies, ERS has been shown to mediate autophagy, a highly conserved cellular degradation mechanism to maintain cellular homeostasis in eukaryotic cells, through the UPR to restore ER homeostasis. ERS-mediated autophagy is closely linked to the occurrence and development of numerous viral diseases in animals. Host cells can inhibit viral replication by regulating ERS-mediated autophagy, restoring the ER's normal physiological process. Conversely, many viruses have evolved strategies to exploit ERS-mediated autophagy to achieve immune escape. These strategies include the regulation of PERK-eIF2α-Beclin1, PERK-eIF2α-ATF4-ATG12, IRE1α-JNK-Beclin1, and other signalling pathways, which provide favourable conditions for the replication of animal viruses in host cells. The ERS-mediated autophagy pathway has become a hot topic in animal virological research. This article reviews the most recent research regarding the regulatory functions of ERS-mediated autophagy pathways in animal viral infections, emphasising the underlying mechanisms in the context of different viral infections. Furthermore, it considers the future direction and challenges in the development of ERS-mediated autophagy targeting strategies for combating animal viral diseases, which will contribute to unveiling their pathogenic mechanism from a new perspective and provide a scientific reference for the discovery and development of new antiviral drugs and preventive strategies.

Investigation of endoplasmic reticulum stress-regulated chaperones as biomarkers in idiopathic non-obstructive azoospermia.

Azoospermia is a condition in which sperm cells are completely absent in a male's ejaculate. Typically, sperm production occurs in the testes and is regulated by a complex series of cellular and molecular interactions. Endoplasmic reticulum (ER) stress arises when there is deviation from or damage to the normal functions of the ER within cells. In response to this stress, a cascade of response mechanisms is activated to regulate ER stress within cells. This study aims to investigate the role of endoplasmic reticulum (ER) stress-regulated chaperones as potential biomarkers in male infertility. ER stress associated with azoospermia can manifest in cells such as spermatogonia in the testes and can impact sperm production. As a result of ER stress, the expression and activity of a variety of proteins within cells can be altered. Among these proteins are chaperone proteins that regulate the ER stress response. The sample size was calculated to be a minimum of 36 patients each groups. In this preliminary study, we measured and compared serum levels of protein disulfide-isomerase A1 (PDI1), protein disulfide-isomerase A3 (PDIA3), mesencephalic astrocyte-derived neurotrophic factor (MANF), glucose regulatory protein 78 (GRP78), clusterin (CLU), calreticulin (CRT), and calnexin (CNX) between male subjects with idiopathic non-obstructive azoospermia and a control group of non-infertile males. Serum PDIA1 (p=0.0004), MANF (p=0.018), PDIA3 (p<0.0001), GRP78 (p=0.0027), CRT (p=0.0009) levels were higher in the infertile group compared to the control. In summary, this study presents novel findings in a cohort of male infertile patients, emphasizing the significance of incorporating diverse biomarkers. It underscores the promising role of ER stress-regulated proteins as potential serum indicators for male infertility. By elucidating the impact of ER stress on spermatogenic cells, the research illuminates the maintenance or disruption of cellular health. A deeper understanding of these results could open the door to novel treatment approaches for reproductive conditions including azoospermia.

Organelle Communication with the Nucleus.

Compartmentalization of cellular components is critical to the spatiotemporal and environmental regulation of biochemical activities inside a cell, ensures the proper division of cellular labor and resources, and increases the efficiency of metabolic processes. However, compartmentalization also poses a challenge as organelles often need to communicate across these compartments to complete reaction pathways. These communication signals are often critical aspects of the cellular response to changing environmental conditions. A central signaling hub in the cell, the nucleus communicates with mitochondria, lysosomes, the endoplasmic reticulum, and the Golgi body to ensure optimal organellar and cellular performance. Here we review different mechanisms by which these organelles communicate with the nucleus, focusing on anterograde and retrograde signaling of mitochondria, localization-based signaling of lysosomes, the unfolded protein response of the endoplasmic reticulum, and evidence for nucleus-Golgi signaling. We also include a brief overview of some less well-characterized mechanisms of communication between non-nuclear organelles.

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.

IL-6 signaling accelerates iron overload by upregulating DMT1 in endothelial cells to promote aortic dissection.

Aortic dissection (AD), caused by tearing of the intima and avulsion of the aortic media, is a severe threat to patient life and organ function. Iron is closely related to dissection formation and organ injury, but the mechanism of iron ion transport disorder in endothelial cells (ECs) remains unclear. We identified the characteristic EC of dissection with iron overload by single-cell RNA sequencing data. After intersecting iron homeostasis and differentially expressed genes, it was found that hypoxia-inducible factor-1α (HIF-1α) and divalent metal transporter 1 (DMT1) are key genes for iron ion disorder. Subsequently, IL-6R was identified as an essential reason for the JAK-STAT activation, a classical iron regulation pathway, through further intersection and validation. In in vivo and in vitro, both high IL-6 receptor expression and elevated IL-6 levels promote JAK1-STAT3 phosphorylation, leading to increased HIF-1α protein levels. Elevated HIF-1α binds explicitly to the 5'-UTR sequence of the DMT1 gene and transcriptionally promotes DMT1 expression, thereby increasing Fe2+ accumulation and endoplasmic reticulum stress (ERS). Blocking IL-6R and free iron with deferoxamine and tocilizumab significantly prolonged survival and reduced aortic and organ damage in dissection mice. A comparison of perioperative data between AD patients and others revealed that high free iron, IL-6, and ERS levels are characteristics of AD patients and are correlated with prognosis. In conclusion, activated IL-6/JAK1/STAT3 signaling axis up-regulates DMT1 expression by increasing HIF-1α, thereby increasing intracellular Fe2+ accumulation and tissue injury, which suggests a potential therapeutic target for AD.

Chlorpyrifos-oxon induced neuronal cell death via endoplasmic reticulum stress-triggered apoptosis pathways.

Chlorpyrifos (CPF) is one of the organophosphorus pesticides widely used throughout the world. Epidemiological studies suggested a link between CPF exposure and neurologic disorders, while the molecular mechanisms remain inconclusive. In the present study, we investigated the impacts of chlorpyrifos-oxon (CPO), the major toxic CPF metabolite, on cell apoptosis, and explored possible mechanism associated with endoplasmic reticulum (ER) stress in SH-SY5Y cells. Results showed that CPO exposure induced dose-dependent apoptosis and expression of ER stress-related proteins in SH-SY5Y cells. Pretreatment with 4-PBA (an ER stress inhibitor) effectively inhibited the expression of GRP78, GRP94, p-IRE1α, and XBP1-s, and apoptotic events. Pretreatment with STF-083010 (an IRE1α inhibitor) partially attenuated CPO-induced apoptosis. In addition, CPO exposure significantly evoked the generation of reactive oxygen species (ROS) which could be eliminated by pretreatment of 4-PBA. Of note, buffering the ROS generation with antioxidant NAC had little impact on the expression of p-IRE1α, and only partially attenuated CPO-induced apoptosis. In contrast, co-pretreatment with NAC and STF-083010 effectively inhibited CPO-induced apoptotic events. Collectively, our results indicate that CPO exposure exerts neuronal cytotoxicity via ER stress downstream-regulated IRE1α/XBP1 signaling pathway and ROS generation-triggered apoptosis. These findings highlight the role of ER stress in CPF-induced neurotoxicity, and provide a promising target for the intervention of organophosphate-associated neurodegenerative diseases.

The preventive effects of natural plant compound carvacrol against combined UVA and UVB-induced endoplasmic reticulum stress in skin damage of rats.

The skin is constantly exposed to a variety of environmental stressors, including ultraviolet (UV) radiation. Exposure of the skin to UV radiation causes a number of detrimental biological damages such as endoplasmic reticulum (ER) stress. The ER stress response is a cytoprotective mechanism that maintains homeostasis of the ER by increasing the capacity of the ER against the accumulation of unfolded proteins in the ER. Carvacrol (CRV) is a monoterpenoid phenol found in essential oils with antimicrobial and anti-inflammatory activities. We investigated for the first time in the literature the potential protective role of CRV against combined UVA and UVB-induced skin damage by targeting the ER stress pathway in a rat model. For this purpose, expressions of Grp78, Perk, Atf6, Ire-1, Chop, Xbp1, Casp12, elF2α, and Traf2 genes related to ER stress were analyzed by RT-PCR and protein expression levels of GRP78, ATF6, CHOP, and XBP1 were determined by ELISA assay in tissue sections taken from the back of the rats. As a result of analysis, it was seen that the expression levels of aforementioned ER stress genes increased significantly in the UVA + UVB irradiated group compared to the control group, while their expression levels decreased markedly by supplementation of CRV in UVA + UVB + CRV group. With regard to expressions of foregoing proteins, their levels escalated notably with UVA + UVB application and decreased markedly by CRV supplementation. In conclusion, present study revealed that CRV ameliorates UVA + UVB-induced ER stress via reducing the expression of mRNA as well as proteins involved in the unfolded protein response (UPR) pathway and inducing apoptosis as evidenced from high Caspase12 level.

Endoplasmic reticulum-targeted delivery of celastrol and PD-L1 siRNA for reinforcing immunogenic cell death and potentiating cancer immunotherapy.

The prospect of employing chemoimmunotherapy targeted towards the endoplasmic reticulum (ER) presents an opportunity to amplify the synergistic effects of chemotherapy and immunotherapy. In this study, we initially validated celastrol (CEL) as an inducer of immunogenic cell death (ICD) by promoting ER stress and autophagy in colorectal cancer (CRC) cells. Subsequently, an ER-targeted strategy was posited, involving the codelivery of CEL with PD-L1 small interfering RNAs (siRNA) using KDEL peptide-modified exosomes derived from milk (KME), to enhance chemoimmunotherapy outcomes. Our findings demonstrate the efficient transportation of KME to the ER via the Golgi-to-ER pathway. Compared to their non-targeting counterparts, KME exhibited a significant augmentation of the CEL-induced ICD effect. Additionally, it facilitated the release of danger signaling molecules (DAMPs), thereby stimulating the antigen-presenting function of dendritic cells and promoting the infiltration of T cells into the tumor. Concurrently, the ER-targeted delivery of PD-L1 siRNA resulted in the downregulation of both intracellular and membrane PD-L1 protein expression, consequently fostering the proliferation and activity of CD8+ T cells. Ultimately, the ER-targeted formulation exhibited enhanced anti-tumor efficacy and provoked anti-tumor immune responses against orthotopic colorectal tumors in vivo. Collectively, a robust ER-targeted delivery strategy provides an encouraging approach for achieving potent cancer chemoimmunotherapy.

Piperlongumine, a natural alkaloid from Piper longum L. ameliorates metabolic-associated fatty liver disease by antagonizing the thromboxane A2 receptor.

Metabolic dysfunction-associated fatty liver disease (MAFLD) encompasses a broad spectrum of hepatic disorders, including hyperglycemia, hepatic steatosis, and insulin resistance. Piperlongumine (PL), a natural amide alkaloid extracted from the fruits of Piper longum L., exhibited hepatoprotective effects in zebrafish and liver injury mice. This study aimed to investigate the therapeutic potential of PL on MAFLD and its underlying mechanisms. The findings demonstrate that PL effectively combats MAFLD induced by a high-fat diet (HFD) and improves metabolic characteristics in mice. Additionally, our results suggest that the anti-MAFLD effect of PL is attributed to the suppression of excessive hepatic gluconeogenesis, inhibition of de novo lipogenesis, and alleviation of insulin resistance. Importantly, the results indicate that, on the one hand, the hypoglycemic effect of PL is closely associated with CREB-regulated transcriptional coactivators (CRTC2)-dependent cyclic AMP response element binding protein (CREB) phosphorylation; on the other hand, the lipid-lowering effect of PL is attributed to reducing the nuclear localization of sterol regulatory element-binding proteins 1c (Srebp-1c). Mechanistically, PL could alleviate insulin resistance induced by endoplasmic reticulum stress by antagonizing the thromboxane A2 receptor (TP)/Ca2+ signaling, and the TP receptor serves as the potential target for PL in the treatment of MAFLD. Therefore, our results suggested PL effectively improved the major hallmarks of MAFLD induced by HFD, highlighting a potential therapeutic strategy for MAFLD.

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.

ER-associated degradation ligase HRD1 links ER stress to DNA damage repair by modulating the activity of DNA-PKcs.

Proteostasis and genomic integrity are respectively regulated by the endoplasmic reticulum-associated protein degradation (ERAD) and DNA damage repair signaling pathways, with both pathways essential for carcinogenesis and drug resistance. How these signaling pathways coordinate with each other remains unexplored. We found that ER stress specifically induces the DNA-PKcs-regulated nonhomologous end joining (NHEJ) pathway to amend DNA damage and impede cell death. Intriguingly, sustained ER stress rapidly decreased the activity of DNA-PKcs and DNA damage accumulated, facilitating a switch from adaptation to cell death. This DNA-PKcs inactivation was caused by increased KU70/KU80 protein degradation. Unexpectedly, the ERAD ligase HRD1 was found to efficiently destabilize the classic nuclear protein HDAC1 in the cytoplasm, by catalyzing HDAC1's polyubiquitination at lysine 74, at a late stage of ER stress. By abolishing HDAC1-mediated KU70/KU80 deacetylation, HRD1 transmits ER signals to the nucleus. The resulting enhanced KU70/KU80 acetylation provides binding sites for the nuclear E3 ligase TRIM25, resulting in the promotion of polyubiquitination and the degradation of KU70/KU80 proteins. Both in vitro and in vivo cancer models showed that genetic or pharmacological inhibition of HADC1 or DNA-PKcs sensitizes colon cancer cells to ER stress inducers, including the Food and Drug Administration-approved drug celecoxib. The antitumor effects of the combined approach were also observed in patient-derived xenograft models. These findings identify a mechanistic link between ER stress (ERAD) in the cytoplasm and DNA damage (NHEJ) pathways in the nucleus, indicating that combined anticancer strategies may be developed that induce severe ER stress while simultaneously inhibiting KU70/KU80/DNA-PKcs-mediated NHEJ signaling.

Role of bariatric surgery in improving diabetic cardiomyopathy: Molecular mechanisms and therapeutic perspectives (Review).

Diabetic cardiomyopathy (DCM), a significant complication of diabetes mellitus, is marked by myocardial structural and functional alterations due to chronic hyperglycemia. Despite its clinical significance, optimal treatment strategies are still elusive. Bariatric surgery via sleeve gastrectomy and Roux-en-Y gastric bypass have shown promise in treating morbid obesity and associated metabolic disorders including improvements in diabetes mellitus and DCM. The present study reviews the molecular mechanisms by which bariatric surgery improves DCM, offering insights into potential therapeutic targets. Future research should further investigate the mechanistic links between bariatric surgery and DCM, to evaluate the benefits and limitations of these surgical interventions for DCM treatment. The present study aims to provide a foundation for more effective DCM therapies, contributing to the advancement of patient care.

[Retracted] Salidroside mitigates hypoxia/reoxygenation injury by alleviating endoplasmic reticulum stress­induced apoptosis in H9c2 cardiomyocytes.

Following the publication of this paper, it was drawn to the Editor's attention by a concerned reader that certain of the cell apoptotic assay data shown in Fig. 1D on p. 3763 were strikingly similar to data that had already been submitted for publication in Fig. 3A in different form in another article written by different authors at different research institutes. Owing to the fact that the contentious data in the above article had already been submitted for publication prior to its submission to Molecular Medicine Reports, the Editor has decided that this paper should be retracted from the Journal. The authors were asked for an explanation to account for these concerns, but the Editorial Office did not receive a reply. The Editor apologizes to the readership for any inconvenience caused. [Molecular Medicine Reports 18: 3760­3768, 2018; DOI: 10.3892/mmr.2018.9403].

Betaine alleviates cerebellar endoplasmic reticulum stress and oxidative imbalance in a cuprizone model of multiple sclerosis in rat.

Multiple sclerosis (MS) is the most common demyelinating disease of the central nervous system, especially the cerebellum, with numerous physical and mental symptoms. Oxidative stress caused by inflammation can play a role in the occurrence of this disease. Betaine, a natural methyl donor compound, has potent neuroprotective effects. Here, we investigated the effects of betaine on motor behavior, cerebellar histological changes, oxidative stress response, and endoplasmic reticulum stress in a cuprizone (CPZ)-induced multiple sclerosis model in male rats. Twenty Wistar adult male rats were randomly divided into four groups including control, MS, betaine-treated MS, and betaine groups. MS was induced by feeding animals with rodent chow containing 0.5% CPZ for 12 weeks. Betaine was daily administrated as 1% in drinking water for the last 6 weeks. The motor behavioral performance was evaluated by open field, rotarod, and reverse basket tests. Histological analysis of the cerebellum was performed by hematoxylin and eosin (H&E) and Cresyl violet (Nissl) staining. Oxidative stress factors (GSH, GSSG, GPX, GR, and GT) were assessed in the experimental groups and finally, the expression of ERS-associated proteins was measured using western blot analysis. Data showed that treatment with betaine could effectively prevent and reverse the adverse behavioral manifestation compared with the MS group. Betaine treatment protected cerebellar demyelination and neuron and Purkinje cell degeneration against CPZ-induced demyelination. Betaine attenuated the protein levels of ESR-related proteins in the cerebellum of MS rats and similarly increased the level of enzymes related to antioxidants in the cerebellum. Therefore, our results suggest that oral administration of betaine may be used as a novel adjunct therapy against cerebellar dysfunctions in an animal model of MS.

Lactobacillus delbrueckii alleviates lipopolysaccharide-induced muscle inflammation and atrophy in weaned piglets associated with inhibition of endoplasmic reticulum stress and protein degradation.

Pro-inflammatory cytokines in muscle play a pivotal role in physiological responses and in the pathophysiology of inflammatory disease and muscle atrophy. Lactobacillus delbrueckii (LD), as a kind of probiotics, has inhibitory effects on pro-inflammatory cytokines associated with various inflammatory diseases. This study was conducted to explore the effect of dietary LD on the lipopolysaccharide (LPS)-induced muscle inflammation and atrophy in piglets and to elucidate the underlying mechanism. A total of 36 weaned piglets (Duroc × Landrace × Large Yorkshire) were allotted into three groups with six replicates (pens) of two piglets: (1) Nonchallenged control; (2) LPS-challenged (LPS); (3) 0.2% LD diet and LPS-challenged (LD+LPS). On d 29, the piglets were injected intraperitoneally with LPS or sterilized saline, respectively. All piglets were slaughtered at 4 h after LPS or saline injection, the blood and muscle samples were collected for further analysis. Our results showed that dietary supplementation of LD significantly attenuated LPS-induced production of pro-inflammatory cytokines IL-6 and TNF-α in both serum and muscle of the piglets. Concomitantly, pretreating the piglets with LD also clearly inhibited LPS-induced nuclear translocation of NF-κB p65 subunits in the muscle, which correlated with the anti-inflammatory effects of LD on the muscle of piglets. Meanwhile, LPS-induced muscle atrophy, indicated by a higher expression of muscle atrophy F-box, muscle RING finger protein (MuRF1), forkhead box O 1, and autophagy-related protein 5 (ATG5) at the transcriptional level, whereas pretreatment with LD led to inhibition of these upregulations, particularly genes for MuRF1 and ATG5. Moreover, LPS-induced mRNA expression of endoplasmic reticulum stress markers, such as eukaryotic translational initiation factor 2α (eIF-2α) was suppressed by pretreatment with LD, which was accompanied by a decrease in the protein expression levels of IRE1α and GRP78. Additionally, LD significantly prevented muscle cell apoptotic death induced by LPS. Taken together, our data indicate that the anti-inflammatory effect of LD supply on muscle atrophy of piglets could be likely regulated by inhibiting the secretion of pro-inflammatory cytokines through the inactivation of the ER stress/NF-κB singling pathway, along with the reduction in protein degradation.

Potential mitochondrial ROS-mediated damage induced by chitosan nanoparticles bee venom-loaded on cancer cell lines.

Recently, numerous studies have confirmed the importance of chitosan nanoparticles (CNP) as a viable drug delivery carrier for increasing the efficacy of anticancer drugs in cancer treatment. It is a macromolecule and natural biopolymer compound, more stable and safer in use than metal nanoparticles. Bee venom (BV), a form of defense venom, has been shown to have anti-tumor, neuroprotective, anti-inflammatory, analgesic, and anti-infectivity properties. Moreover, the regulation of cell death has been linked to reactive oxygen species (ROS)-mediated cell apoptosis, which induces mitochondrial damage and ER stress through oxidative stress events. Therefore, this study aimed to illustrate the ROS-mediated effect on the cancer cells treatment with CNP-loaded BV (CNP-BV) and explained the adverse effects of ROS generation on Mitochondria and ER. We have found that the targeted CNP-BV were high in cytotoxicity against MCF-7 (IC50 437.2 µg/mL) and HepG2 (IC50 109.5 µg/mL) through the induction of massive generation of ROS, which in turn results in activating the mitochondrial cascade and ER stress. These results highlighted the role of ROS generation in inducing apoptosis in cancer cells.

The Role of Endoplasmic Reticulum Stress on Reducing Recombinant Protein Production in Mammalian Cells.

Therapeutic recombinant protein production relies on industrial scale culture of mammalian cells to produce active proteins in quantities sufficient for clinical use. The combination of stresses from industrial cell culture environment and recombinant protein production can overwhelm the protein synthesis machinery in the endoplasmic reticulum (ER). This leads to a buildup of improperly folded proteins which induces ER stress. Cells respond to ER stress by activating the Unfolded Protein Response (UPR). To restore proteostasis, ER sensor proteins reduce global protein synthesis and increase chaperone protein synthesis, and if that is insufficient the proteins are degraded. If proteostasis is still not restored, apoptosis is initiated. Increasing evidence suggests crosstalk between ER proteostasis and DNA damage repair (DDR) pathways. External factors (e.g., metabolites) from the cellular environment as well as internal factors (e.g., transgene copy number) can impact genome stability. Failure to maintain genome integrity reduces cell viability and in turn protein production. This review focuses on the association between ER stress and processes that affect protein production and secretion. The processes mediated by ER stress, including inhibition of global protein translation, chaperone protein production, degradation of misfolded proteins, DNA repair, and protein secretion, impact recombinant protein production. Recombinant protein production can be reduced by ER stress through increased autophagy and protein degradation, reduced protein secretion, and reduced DDR response.

Time-Dependent Potentiation of the PERK Branch of UPR by GPR68 Offers Protection in Brain Ischemia.

BACKGROUND: In ischemia, acidosis occurs in/around injured tissue and parallels disease progression. Therefore, targeting an acid-sensitive receptor offers unique advantages in achieving the spatial and temporal specificity required for therapeutic interventions. We previously demonstrated that increased expression of GPR68 (G protein-coupled receptor 68), a proton-sensitive G protein-coupled receptor, mitigates ischemic brain injury. Here, we investigated the mechanism underlying GPR68-dependent protection. METHODS: We performed biochemical and molecular analyses to examine poststroke signaling. We used in vitro brain slice cultures and in vivo mouse transient middle cerebral artery occlusion (tMCAO) models to investigate ischemia-induced injuries. RESULTS: GPR68 deletion reduced PERK (protein kinase R-like ER kinase) expression in mouse brain. Compared with the wild-type mice, the GPR68-/- (knockout) mice exhibited a faster decline in eIF2α (eukaryotic initiation factor-2α) phosphorylation after tMCAO. Ogerin, a positive modulator of GPR68, stimulated eIF2α phosphorylation at 3 to 6 hours after tMCAO, primarily in the ipsilateral brain tissue. Consistent with the changes in eIF2α phosphorylation, Ogerin enhanced tMCAO-induced reduction in protein synthesis in ipsilateral brain tissue. In organotypic cortical slices, Ogerin reduced pH 6 and oxygen-glucose deprivation-induced neurotoxicity. Following tMCAO, intravenous delivery of Ogerin reduced brain infarction in wild-type but not knockout mice. Coapplication of a PERK inhibitor abolished Ogerin-induced protection. Delayed Ogerin delivery at 5 hours after tMCAO remained protective, and Ogerin has a similar protective effect in females. Correlated with these findings, tMCAO induced GPR68 expression at 6 hours, and Ogerin alters post-tMCAO proinflammatory/anti-inflammatory cytokine/chemokine expression profile. CONCLUSIONS: These data demonstrate that GPR68 potentiation leads to neuroprotection, at least in part, through enhancing PERK-eIF2α activation in ischemic tissue but has little impact on healthy tissue.

Analysis of Unfolded Protein Response Activation in Colon Adenocarcinoma Epithelial Cells: A Proteomic Study.

PURPOSE: High throughput technologies have identified molecular patterns in colorectal cancer (CRC) cells, aiding in modeling responses to anti-cancer treatments. The different responses observed depend on the type of cancer, the tumour grade and the functional programme of the cancer cells. Recent studies suggest that the unfolded protein response (UPR), autophagy and apoptosis could be involved in treatment resistance mechanisms by interacting with the tumour microenvironment (TME). EXPERIMENTAL DESIGN: We analysed by LC-MS/MS the proteome of two representative colon adenocarcinoma epithelial cell lines from different tumour grades (CCL-233 and CCL-221) at the basal state or after the UPR induction. RESULTS: Cell lines expressed a different proteome on about 10% of their total proteins identified, especially on UPR, autophagy and apoptosis pathways proteins at basal state. After UPR induction, the proteome of the cells was modified with a greater adaptive response to cellular stress in CCL-221 cells where the UPR was strongly activated at the basal state. CONCLUSIONS AND CLINICAL RELEVANCE: CRC cell lines at different tumour grades expressed different functional programmes at the proteomic level and were characterised by different responses to the UPR induction. This study suggests that baseline cancer cell stress status could have an impact on the efficiency of cancer therapies.

miRNA omics reveal neferine induces apoptosis through Ca2+mediated endoplasmic reticulum stress pathway in human endometrial cancer.

BACKGROUND: Endometrial cancer (EC) as one of the most prevalent malignancies in the female reproductive system, usually has a poor diagnosis and unfavorable health effects. Neferine (Nef), derived from the edible and medicinal lotus seed, has been known for its functional activity; however, its anti-cancer mechanism for EC remains elusive. PURPOSE: We explored the potential anti-cancer effects and underlying molecular mechanisms of Nef on EC. METHODS: The cytotoxicity was tested using MTT, and the cell cycle, apoptosis, Ca2+ levels, and the mitochondrial membrane potential (MMP) were observed through flow cytometry. After Nef treatment, differences in miRNA expression were identified using miRNA-seq data. Furthermore, western blot and immunohistochemistry (IHC) were employed to identify the proteins associated with apoptosis in both mice and cells. RESULTS: Nef treatment led to Ishikawa cell apoptosis and blocked cell proliferation in the G2/M phase. In total, 101 significantly different miRNA (p 〈 0.05 and |logFC| 〉 1) were obtained and subjected to GO and KEGG enrichment analysis, which revealed the Ca2+ and PI3K/AKT signaling pathways pertaining to apoptosis. Nef treatment significantly changed intracellular Ca2+ levels and MMP, activating the endoplasmic reticulum stress (ERS) pathway and the expression of key proteins in the mitochondrial pathway. In addition, Nef also inhibited the expression of key proteins in the PI3K/AKT pathway, causing cell apoptosis. Moreover, in mouse tumor tissues, the expression of CHOP, Bcl-2, Caspase 3, Cyto-c, and p-AKT was also consistent with the results in vitro. CONCLUSION: Nef could block the cell cycle and induce the activation of the mitochondrial apoptotic pathway involving the Ca2+-mediated ERS pathway and the PI3K/AKT pathway, thereby inducing apoptosis in EC cells, confirming the potential role of Nef in the prevention and treatment of EC.